I agree that 1 and 2 are the ways to go. Of course, if Guy 2 is wrong, the worst you do is call him back to install a second system on the first floor. Since the two are totally separate, it won't save you much to do it all at once.

FWIW, we did what guy 1 said, although we also have the "attic" as a living area with A/C.

Thank you both - I appreciate the input. As far as our summers, we are in Buffalo NY - summers are fairly temperate with about 10 or so days where it's 90 degrees and muggy and you're dying for a/c, and much of the rest of the year you're fine without it. But I don't want to spend several thousand dollars to install a system and then have it not be effective on those 10 days.

I agree that 3 and 4, especially 4 should not be considered, since hot water heating is vastly superior and more efficient than hot air heating.
However, since you are talking only about 10 days and assuming you spend most days and evenings downstairs, it would make the most sense to do that first with the basement ducting and consider a few window units upstairs, if needed.Or opt later for the second unit if you are still not satisfied.Dropping cold air down using #2 in my view is problematical and if it doesn't do a good job, you are stuck with an oversized unit for the upstairs. which will make the total job more costly and will not be very good.
BTW,I had a similar house in Connecticut where it is a lot warmer than Buffalo and used an attic fan at night ( most nights are cool)to comfortably cool the sleeping area.2 large sleeve units (which we inherited) noisily cooled our downstairs area. I was thinking of changing to central air for the downstairs, when my wife decided it was time to move.

Actually, I'm thinking that for a Buffalo application, a minisplit system with individual room air handlers might be the way to go.

Far less disruption to the envelope of the house.

No, not quite as good as far as terms of coverage, but overall not bad.

And, given that you're in Buffalo, NEVER get rid of your baseboard hot water! NEVER!

Do not go with the mini split systems, not because they won't work well, but because each air handler sticks out about 8" off the wall.
The best way to go would be the seperate systems for the upstairs and downstairs. You will be able to condition the spaces seperately, and you will be much happier with the outcome.

I agree with tlewis hvac and if you don't listen then by all means stay away from the Mitsubishi line, especially the multi evap models. To complicated and exotic and way overcontrolled for a residential system. It may cause you aggrivation or loss of spare finances.
For my money I'd pick door number one. In order to remove moisture from the air you have to pass that moist air across the evap coil of the air conditioner. So unless he plans on installing adequate returns to your lower floor there is no way that cool air trickling down your stairway is going to feel comfortable on a hot humid day. And returns are useless without supply registers. I think door number two isn't much sharper then 3 or 4 when it comes to A/C!

I live mid-CT and have set up #3 single zone for a 2 story colonial around 2400sqft with air handler in the basement. i was very worried but it works w/o any problems during the summer. the system gets my home down to 69-70 when i want to be freezing. im no expert but given the short summers do you really need 2 zones.

have they done a manual J to determine cooling needs?
ignore #4. i think hot water heat is the best and wouldnt trade it.

good luck.

Re: metromom

WeÂve just completed a retrofit in a home that had/has radiant heating, no duct work, that now has with one compact geothermal unit, radiant (water) central heating, central cooling (with the same water), AND domestic hot water at a tremendous energy savings. Each new heat exchanger is individually controlled creating multiple zones throughout the entire home.

This no doubt is a high-end system. However, youÂre looking at spending a lot of money anyway for what you want to do. So forget Guys # 1 ~ 4, forget ducts and forced air and think geothermal (the most efficient & greatest added value and comfort to your home) and think water which you already have!

IMPO

SR