Two stage systems are for encreased comfort and more energy savings, but a non-two stage system with a VS (variable speed) indoor unit will suffice just fine in your area. *I checked the load condition of your area and a VS would be helpful to you.
A VS system will not cure the upstairs downstairs temperature problems, only having two systems (one up, one down) will satisfy these requirements or designing in a zoneing system ducting and dampers will help. These are the truly two options that are effective and I always lean more to the two systems.
Don't worry about the type of refrigerant, R22 and R410A are both designed for the systems they are used in and both do the same job.
Builders get away with putting one system in a two story home and I think (I know) it is a shame they decide to save money and pass the problems on to the buyer.
I know it's costly but have a contractor do a load on the upstairs and the downstairs and size two systems to correct the problem or it will not go away.
But I'll bet you have already heard this before.

Most 20 year old homes in our area only have one unit. I do see newer homes have two sometimes three. I have to believe there is some way to get the upstairs cool without having the downstairs freeezing, other older homes have done it.

I just want to make that variable speed will not make things worse up there by blowing less!!!

You seem to have the same problem I do. The house wasn't built with central A/C in mind, so your ducting isn't big enough and you don't have enough return vents upstairs.

Yes there is a way to balance between upstairs and downstairs, but I would imagine that the homes you see with 1 system are probably all either too hot or too cool upstairs. Once again, the time needed to balance between the floors is many hours. Unless the HO wants to invest the time over a couple of years, it will always be wrong. I cannot imagine adjusting airflow without a meter either. When I adjusted my house many years ago, (1985) It was ongoing process for a year. The next year, I had to argue with the family to leave the registers alone. 3 women and me.

Variable speed reduces cooling capacity greatly, when the blower is at half speed. Most blowers average at about ½ to 5/8 speed. This means the system has to run longer to do the same job.

The longer it runs, the less efficient it is. The more it costs to operate. Variable speed is a whiz-bang of the 2000Âs at this time. Kinda like the pet rock craze. It can have some benefits, but the cost to the HO is a personal adjustment that may or may not be good.

Heating blower fan speed is usually at the lowest speed. I cannot imagine that the variable speed blower will help much if it runs at a higher speed. Variable speed is for Air-conditioning.

"...your ducting isn't big enough."
- Let's not make personal comments.

My home, as all in our development, was designed for central air...it is not an afterthought. I have not added any new ducts or anything of the sort. Each room upstairs has a duct. You can feel the air getting sucked in when you put your hand by it. I am guessing that somewhere are dampers for the upstairs that may be closed but I have not been able to find them. Then again, there does appear to be good air flow thru the registers up there so I am not so sure why it is so much warmer. I guess its normal to set your thermostat at 65 on the first floor to cool the second in a 20 year old home....though this is the first one I have experienced that with.

I was told the variable speed provides more comfort in the winter since it blows longer but with less force, that way on those cold nasty nights you do not feel the less than hot heat pump air blasting you as much. My fear is that if its hot upstairs already in the summer, it will only get hotter with less air coming out the register.

Sounds like folks are saying the same two things:

1) Variable speed will make me more comfortable and is more efficient---still no explanation as to how...

2) Variable speed is a gimmic that actually costs more to operate.

If only I could get the answer...choosing wrong could set me back another $1k!

"Variable speed will make me more comfortable and is more efficient---still no explanation as to how"

- In the summertime, a fan running on lower speed for longer times pulls more humidity out of the air. In the winter using the heat pump, you don't get the blast of cold air at start-up because the fan gradually ramps up. These are the "more comfortable" part. Since it is a DC (direct currrent) motor, it costs less to run than the typical AC (alternating current) motor. This is the "more efficient" part. Not sure that the variable speed motor will help you at all with floors seeing different temperatures as Daddo stated previously. Ceiling fans will help this and so will running the furnace fan all the time in the summer. The key is to circulate air thru the house to try and equalize temperature.

"Variable speed is a gimmic that actually costs more to operate."

- This is Bob Brown's opinion. They cost more to repair for sure, but you have to do some experimenting to figure if they cost more (based on run time, power consumption, and cooling effect).

I chose not to get a variable speed with my new heat pump. The air handler that I bought has 3 fan speed settings so I get to play with only 3 speeds. The Goodman variable speed air handler has dip switch settings for 4 fan speeds for each mode: heat pump/ac, heat pump + electric back-up, and electric emergency only. It also has a trim adjust dip switch of +15% or -10% CFM for the 4 settings for each of the 3 modes. For this variable speed motor, running the unit in "fan only" on the thermostat sets the fan speed at 30% of the heat pump/ac setting. You get a lot more to play with with variable speed motors.

Hope this helps.

hmmm, might my 20 year old trane have speeds other than the one its currently running at...where would I look?

Yes, it probably does.

There is a minimum required fan speed if you have electric back-up heat in the air handler. You are thinking about increasing the fan speed to get more A/C.

You have to know what you're doing inside that air handler box or you risk damage to the unit or worse, to you, Andre. Not recommended for the inexperienced. If you do, make certain that power from the house breaker is killed plus the breaker that may be on the air handler itself is killed before you open the blower door cabinet and snoop around.

If you have a 3 speed fan motor, which you probably do, there should be a schematic inside the blower door area showing the color of wire that controls the fan speed (ex: red = low, blue = medium, black = high). The wire to be switched is usually not on the motor itself but on a circuit board or at a terminal block. There wire that's controlling the fan speed will be near the other 2 but at a different terminal.

For the a/c system to operate properly, the static pressure in the ducting should be checked with the specs on that system. Changing the blower speed can hurt you more than help if the cfm is changed in relation to the static psi.
VS motors are very efficient and they don't have to be dedicated to one setting. Static pressures in the duct can be fine tuned to meet just about any demand- if the ducts are sized properly.
I met a women today who has one system in her two story home (trane- 15 years old) and she is happy with the upstairs/downstairs temperatures. I checked and found a simple 80%/20% damper system with two thermostats and two dampers which place 80% upstairs or downstairs, depending on the call from either thermostat (20% goes to the uncalled area). A primitive setup by todays terms- but obviuosly effective. This system was designed though when the home was built and the duct sized accordingly.

I am now thining that I get the HVAC company that gave the system replacement proposal in and try to make some adjustments. Maybe whatever I pay can be deducted from my bill if I make the $7K purchase thru them later this summer.

I just hate to spend the $7K and end up with either a freezing lower floor or hot upper floor. Also, I really wanted to wait until August so I could see what my bills are.

Not to be a whimp but I felt comfortable adjusting the dampers though I could only find the runs thru the basement to the first floor. I can not find the ones going upstairs so if they have dampers I will never know!

If it were a simple 3 speed switch with a knob I could handle that...moving wires....not me.

I think its a couple of degrees cooler upstairs since I closed off the dampers downstairs. Funny, I'd say I shut them all back about 80% too. Still, it seams to be at least a 6 - 8 degree difference, its hard to tell because one day it 85 the next 65.

Also, now that I adjusted the dampers, althought the unit still cycles on/off and I assume the cycle is longer, the house feels more humid...maybe it my imagination but is that possible?

Andre:

Can you install ceiling fans in the upstairs bedrooms??

Have you tried running the furnace fan all the time when its hot outside??

Possibly yes in bedroom fans but then you have a draft on you...worst case scenario, it possible. I notice when the weather is in between and I leave the fan on, it gets stale in the house. I'd imagine that once the hot weather is here to stay that would work well since I did that in my old home.

Could closing off the dampers on the first floor make the house feel more humid. The unit cycles on/off but I'd swear its more humid now.

have you looked at the duct work..or has any of the hvac companies commented on the install of the ductwork?
excessive ductleakage may be a factor also.
if your ducts are 'sealed' with duct tape, you have excessive leakage. mastic is used for long lasting seals whereas duct tapes fail is a short time.
not vs or 2 speed related..just another factor..like you needed another!!

bottom line...I need an HVAC to take a look and I think I will get the company whos estimate on a eventual replacement unit to bet the ones...that way they know wht they are getting into if they do the eventual job. Thanks all.