Yeah ive seen people doing that but S6 brakes arent exactly easy to come by and to be honest they are great. The reason I ask is I looked for ages for information about brake upgrades for the C6 platform and the only thing i could find apart from put EBC ***** pads on the OEM calipers was S6 calipers and discs as youve mentioned. Ive just fitted Audi 8 pot calipers to mine using the Rs4 fully floating discs my car is running Lambo/RS4/RS3/Phaeton 8 piston calipers and 365mm fully floating discs, either plain or punched. The set up works really well if you know what carrier, disc and bell to use.