I do not know which brand you should pick. But your mention that air flow from some of the vents is inadequate suggests to me that you should have someone really competent give you an opinion on what needs to be done to balance your system so that heated/airconditioned air is distributed evenly throughout your house. You may need alterations in your vents to achieve that goal.

Why do you think Lennox is not good now? I wouldn't necessarily take Lennox out of the question. Trane's spine fin coils can be difficult to clean with cotton weed, so you'll probably want to stick to brands like Rheem, Lennox, Carrier, etc. The Infinity is a nice system, but you can still spend less to get a nice system with many similar capabilities. I've never been a huge proponent of the Infinity system unless someone really thinks they'd need all the bells and whistles. Similar results can be achieved with the right system for often a lesser price.

That's cool advice - I just heard from a range of people that Lennox is no longer a trusted name--that and there are few parts distributors here in Kansas, which could make repairs time-consuming and costly.

I do have artwork in my house, so being able to regulate humidity is important--and it sounds like the Infinity system lets you regulate those sorts of things. Any ideas on what I could expect to spend for such a system? I think I have about 2000 sq ft...

I've seen Infinity quotes range anywhere from the upper $7000 range to $10k and upwards. If humidity control is important, I'd suggest you look into getting a properly-sized system according to a load calculation and a control with which you can set a humidity setpoint--whether you choose the Infinity or another system. A 2-stage system may be beneficial in your application for added humidity control.

By the way, I took a class in art history and found it very interesting, even though I didn't convert it into a career. I assume by your name this is a point of interest for you.

Upgrade your thermal envelope ie your insulation and airsealing before you invest in a system. Capes always have issues with this and if you do you might find you will need a smaller system thats alot cheaper to buy and run.

Sounds like good advice! I like the interface with the Infinity but it's almost a case of Cadillac vs. Hyundai when both will do a great job of basically getting you from A to B. That's why I wanted to know what systems to go for or stay away from. I am not sure it is WORTH $7000 for a system in a relatively compact home, or whether it would pay for itself in the long run.

Also, in terms of quotes/bids, how do I ensure I get the price as low as possible? Are there tricks to the trade in the bidding process? Anything I can say for instance to get them to come lower?

And yes I teach art history - I find the complexities of HVAC to be thoroughly intriguing, too! Not to mention my odd obsessions with airplanes and 5-cylinder automobiles... :-)

When looking at the Infinity and other "2 stage" systems, the comfort is what should be the selling point, not necessarily the return on your investment. It will be more efficient, yes, but the higher-efficiency units don't necessarily pay for themselves given the upfront cost.

As far as bringing the bids down as low as possible within reason, I'd be careful with this only because you don't know what corners, if any, will be cut. Some companies have room to go a little lower; some will end up taking shortcuts to cut their ultimate cost. Sometimes sharing your price from another company will cause them to match that price and maybe more. It all depends on the trust you have in the sales rep. A good, reasonable and reputable company should already have a reasonable price.

If you're looking for a good system without the bells and whistles and within a reasonable cost range, I'd look at 14-15 SEER A/C units with with furnaces with variable speed blowers to help with humidity, efficiency, and overall comfort. You can also get a thermostat with the ability to control the blower speed to dehumidify.

In addition to above, another way perhaps negotiate the price you received would be to say something along the lines of, "I'm compelled to go with your services and I think you all would do a fantastic job, but the price is a bit higher than I was looking to spend. Can we work something out?"

Of course I'd only do this if you definitely wanted to go with one company or the other and explained that you were ready to sign the contract.

The most important step is a heat loss/heat gain. Oversized unit use more fuel and have more maintenance.
When I worked in the trades and gave a price it was always a fair price. We were one one the most expensive companies in town. If someone asked for a cheaper price I would always ask them how much they wanted to pay. They gave ma a figure and I would tell them let me see what we can take out to get down to that price. The looks I used to get. We charged for what we did and did what we charged for.
There's a rule in our industry, you can have it right, you can have it fast or you can have it cheap. Pick two.
If the company does not do a heat loss find someone else or have a heat loss done so everyone is on the same playing field and does not waste your time.