never mind...it WAS the DRC. Front left strut, to be exact. While no oil ever leaked, and the system was under full pressure, I picked up the old strut rod, and when I grabbed the rod, it wiggled as if it were barely attached.
So there we go. Even without oil leaks, Audi can't build a strut correctly. Did not price out what a replacement front strut would cost, but I'll bet replacing it, plus servicing the DRC, would be costing me a ton more than I'm paying now.
$800 in parts (Konis, H&R springs, some rubber bits, control arms, tie rods), $700 labor, and that's a pretty comprehensive suspension overhaul. Not bad at all!!
Fingers crossed that I'll have now covered all the weak points with the car, and all the tuning I'll have wanted to do is done
Should have 65,000 miles of clear sailing before the big timing belt service needs to be done again.