Groan...here we go again...
6 pot callipers won't give you great brakes...the pistons are too large and there are too many of them to properly match to many Audi master cylinders (the S3s included) so you end up with very long pedal travel and no better brakes...plus your brake balance can be screwed up..
Just because they can be made to bolt up, doesn't mean they are an upgrade!The Cayenne has a HUGE master cylinder compared to the likes of an S3 (something like 26mm vs 23.5mm)
If you want much better brakes, stick to something that
A) fits
B) has spares readily available
C) works
Unless you only want them for show...in which case go right ahead...