Originally Posted by tgrandy2001
I am a Canadian but currently live in Europe in the Baltic states, I will be here for another three or four years.
I guess I would question why you want 20" wheels? The US-market S6 has the combination you describe - air suspension plus (optionally) 20" wheels. I only got to drive my car for 5 days (European Delivery) so I cannot really provide much input but I didn't get any complaints from the wife about harsh ride (keeping ADS in "Auto" most of the time) on 20" Pzeros.
Personally I only picked 20" wheels because the S6's 19" tire size is unusual (at least here in the US) so going to 20" gave me more and cheaper tire options. I'd think something in the 17" or 18" range would yield much better tire sidewall heights but that's very much NOT in vogue now. (My C5 came with 16" which I bumped to 17" to decrease and stiffen the sidewall slightly.)
If you can get the car you want with 18" wheels, that might be a much better choice....