If you have ACC be careful using anyone but audi.
this was a costly experience for me when i used someone to adjust my tracking (they also do my drift car) and it knocked out the ACC - down to audi for tracking and 775 later it was fixed
i use 452's on my A8 255-35-20 they often pop up for £100 on mytyres. so i grab them when they do.
easily the best tyre in that size for £100 anything half decent will cost you £160 minimum,
i prefer the grip of the 452's over the pilot sport 2's dont last as long but at nearly a 1/3 of the price who cares.
Toyo T1'rs are quite cheap in that size, very grippy but dont expect them to last ages. ive got these on the front of the drifter.