Replace 12-yr-old furnace and other ?s

[ColoradoHomeowner]

In 2000, we bought a 1985 home (3,300 sq. ft, 2-story) in Denver and put a new Amana 80% furnace into it. The home had a Rheem AC which was already 8-10 years old and now needs replacing ... at least according to the tech who came out to do an annual maintenance today. We're planning on selling the home within 4-6 years. So here are my questions:

1. Brands. I've heard the installation is much more important than the brand. But I think we've found several good companies to give us quotes. One carries Amana. Another carries Trane, Lennox and EverRest (a Goodman brand, right?) And the other carries Rheem. Installation being equal, which brand would you put in your home?

2. Efficiency. Denver has a pretty short cooling season and we try to use the AC pretty minimally. Do I just go 14 SEER or higher?

3. Furnace too? Our Amana furnace is a tank -- it has run almost flawlessly from Day 1. Considering how long we're keeping this house (4-6 years) would you replace the furnace as well? If so, what level of efficiency?

Thanks so much!

[catmanacman]

Did he state exactly why it needs replacing.

[ColoradoHomeowner]

Did he state exactly why it needs replacing.

Oops. Sorry. I wasn't here when the inspection was done, but the tech indicated several problems to my wife, but they all added up to: this thing is old as the hills (as I said, 18-20+ years) and has a number of components that are on the verge of failure.

Still, we'll be getting our other candidate companies to give us their assessment of whether we can limp along with some fixup instead of replacement.