Which Quattro to buy?

[Jeff Fithian <jfithian@worldnet.att.net>]

I know this is kind of an open-ended question, but I'm considering
buying an Audi and am split between an A4 1.8TQ, an A4 2.8Q, or maybe a
used S4 or even S6.  Any comments on the relative pros and cons?
Experiences?  What about things like chip upgrades, especially in the
case of the 1.8T?  Any comparison between the '97 and '98 2.8L engines?
How about the reliability of an older S4?  Will I have to worry about
unintended acceleration??  Just kidding :-).  Any help would be
appreciated!
Thanks
Jeff

p.s. Are there any members who live in Boulder, CO?  Any kind of Quattro
club out that way?