I have only used these non-grooved brembo discs like the stock car, they have been fine. Check stealer price but I doubt they can do better.
I see now brembo is offering grooved and drilled discs for a D2 S8. Haven't tried those.
http://www.ebay.co.uk/itm/Front-Brem...item4cff2cb505
Also I only use brembo pads too.
http://www.ebay.co.uk/itm/AUDI-A8-S8...item460a88c5e2