80k vs 100k btu furnace

I plan to replace two sets of systems(AC+furnace+coil), that is two zones in my house(in Maryland). One system covers the 2nd floor(furnace in attic), and one bigger system covers the 1st floor and basement(finished) with another furnace in basement. For the main/bigger furnace, currently I have 23-year-old York with 92K btu furnace( in basement, 21" width), cover ~2000ft 1st floor and ~1500ft finished basement. One contractor gave me a quote for 100K btu, but another contractor suggested 80K btu(when I asked why 80K, he just said 100K would overkill). I decided to go with single stage only, not the two stage models. The price difference for the upgrade(80K -> 100K) is only $200. Considering energy saving and noise, is 80K better than 100K? Could it be a problem to downsize the furnace for future house sale(which may give buyer an excuse to ask for replacement)? What would you suggest, 80K or 100K? Please advise. Thank you!

BTW, one contractor sells me Trane(their low end XR14), the other contractor sells me American Standard(also low end Silver model), for similar price(the American Standard set just about several hundred cheaper than the Trane set). Some people said they are the same thing, is that true? How about part supply, part cost and service cost in the future? Please advise as well. Thanks again!!

 

Best not to oversize a furnace. I had a 40 year old York. Also close to 95k.
I opted to replace it with the 80k and it was perfect.
It actually ran less than the furnace it replaced.
Calculations can be made for exact sizing.

Trane is a subsidiary of American Standard. Basically same mfg.

 

Hi Pete,

I tried to use the sizing tool at https://www.pickhvac.com/furnace/sizing/, however, I found it way "oversized". I did "zone 4" and "3500 sq ft", I got "Recommended 80% AFUE Furnace Size: 169,000 BTU"! You are expert, if you think I can downgrade my main 80% AFUE furnace from 92K to 80K, I will take your advice. I assume with less BTU, the furnace will be more quiet(furnace only or both furnace and blower for noise?) and use less gas for long run, is that right?

About Trane vs American Standard, can their parts exchangeable during future repair? Thanks!