Newer Audi buyers guide? Advice requested.

[blarson at Zeiss.com]

I have been looking in the paper lately, and have noticed that the prices
on 1996-2000 A4Q and A6Q cars are getting pretty reasonable.  Does anyone
have advice about the purchase of these cars used?  I have a lot of info
about 5 cylinder cars longevity wise, but not about the newer stuff.

Here is what I would like to buy to replace my wifes 5ktq.
a4q or a6q (1996 or newer)
Must have quattro and a manual transmission
Open to any engine (but faster is better of course)
Must have leather heated seats (to her this is a dealbreaker)
price range $5k-12k
mileage under 100k

There are 4 cars as described above here in the twin cities for $5-8k right
now, so they are out these for a reasonable price.

My questions are these,
Motors to avoid?
Models to avoid?
Model years to avoid?
Engine longevity?  Are any of the newer cars over 200k miles yet?  Any
problems with oil consumption?
Drivetrain reliability?  How many miles are the newer quattro manual
transaxles good for?
Common failures?
1.8t vs 2.8-12v vs 2.8-30v, which is the best engine overall for
power/mileage/longevity.
Body rust resistance, trim quality, interior durability.

Thanks for the help.
Brian