To be honest, it depends how you drive, as to what advice is best.
The fastest way to get a FWD around a track is to use as much weight transfer as you can get over the front wheels, so that means the rear brakes are used for control rather than stopping and you run as small and light as you can. You sling all the power to the front to get weight on those wheels, which equals turn-in grip. Once you're confident enough to go in faster on trail braking, using the oversteer that come with it, you'll see why. It's pretty much why French cars are fast. I ran 343mm Alcons and standard rears, pretty much like the VWCup cars run - I never had an issue.
That said, lots of people don't like this kind of setup and want something more 'planted'.. hence the S3 rears. Fair enough, but don't be tempted to run uprated rear pads, as without a brake bias valve you'll never get enough heat into them to use them effectively, OEM are more than adequate.
