My furnace has been determined to be unrepairable. Giving the HVAC
contractor the benefit of the doubt for now and assuming he's correct
in this determination (I'm willing to believe it - rusted out heat
exchanger, rusted out burners, bad blower motor, furnace is approx 15
yrs old with some obvious water damage in and around the heat
exchanger).

The house is unoccupied right now while we're doing rennovations and
will probably remain so for the next 2 months or so, so I have the
luxury of some time to look for a good but affordable furnace and
contractor - though sooner is better since drywall mud dries VERY
slowly in a cold house. Here are my needs/wants/ideas, please comment:

1) the house is approximately 1500 sq ft of living space, about 1000 of
that is original, 2 1/2 story, 1920's, uninsulated construction (the
rest is a single story addition with 2x4 walls and fiberglass
insulation).

2) single pane storm windows throughout most of the house (I plan to
eventually fix the insulation and windows when money and time allow,
but the furnace is an immediate problem obviously)

3) The house has a brick/masonry chimney, at what efficiency rating is
a PVC liner required (or am I wrong in thinking it's required at all?)?

4) I think a multi or variable speed blower would be beneficial,
comments? worth the extra cost?

5) Is a two-stage burner worth the extra cost?

6) the current AC system appears to be an add-on system with an a-frame
shaped evaporator installed into the supply plenum above the furnace
(might have contributed to the water problems that rusted this unit
out). I don't have the funds to replace this, but I might be able to
re-install it properly if it is not currently right.

7) fuel is natural gas, installation is in the basement (unfinished -
unlikely to ever be finished)

8) there is no filtration on this current unit, I'd like to add one but
have not yet decided what type - leaning towards a basic, paper filter
type. No major allergies in this household (some seasonal pollen
allergies, minor)

Anyway, those are what I'm looking for in features. I've looked at
Trane, Rheem websites so far and will keep trying to educate myself
here. I'm also contacting local contractors to get quotes but haven't
received any yet.

Thanks in advance for advice.