If there is a hole or crack in the heat exchanger, anyone servicing the
unit has an obligation to turn the gas off, red tag it, and document it
with the owner's signature on it. If that is not done, and later when
there is a fire or CO problem, guess who will be held responsible.
Does the Amana estimate include the evaporator coil? If not, it is
nearly $1000 more that the Trane. Amana IMO makes a good furnace, but
it is really pretty much a Goodman. Assuming the same quality of
instalation, I would expect it to be somewhat less than a Trane, not $1k
more. Whether to go with 80% or 90% all depends on where you are
located. I am in S.Tx and there are probably not a dozen 90's here. Up
north, a 90 would be the only thing to conside.
As always. the installation is the most important part of the equation.
Make sure the installer pulls a permit and gets all the proper
inspections done. This is important in any situation, but with you
planning on selling the house relatively soon, it will almost certainly
bite you in the butt if you don't. Larry