V8 Newbie

[Michael Cohen <mcohen@micron.net>]

I've just acquired my first Audi after many years of Saab/VW/BMW.  It's
a '90 V8 Quattro, automatic, comfort seats, burnt sienna (sort of
orange-burgundy) on black, 46,000 actual miles, full service records. 
Aside from a few scuffs and some wheel scrapes the car is in perfect
shape; the original owner used a second set of floor mats to protect the
factory floor mats, and cried when I drove her car away.

Purchase price was $13,000.  I'm now considering what service and
upgrade investments make sense.  After browsing the archives for several
days I've become concerned about the timing belt.  Should I replace at
this time due to age rather than wait for 60K?  Tires are GY Eagle GA,
on factory wheels.  Would 16x7 BBS RZ II, Pirelli P7000 SS 225/50 x 16
be a smart move?  That's the only wheel Tirerack listed.

My first few days with the car leave the impression that the platform
could benefit from both power and suspension improvements.  Does anyone
have experience with upgrades such as spring/strut combos, Q-Chip,
custom exhaust, cams etc?  I don't want to ruin the poised and
comfortable ride, just firm things up a bit.

This is the first auto trans for me.  Is it insane to be thinking  about
upgrades like this on a two-ton luxury car?

MC  '90 V8 Quattro
    '89 Toyota 4x4 PU  (Idaquattro)