i'm running the porsche 944 setup, which means 11.5" rotors on all fours corners. they're cheaper because you can pull them from a junkyard, and you wind up with easily upgradeable parts. my wheels are porsche boxster s wheels, mostly because the porsche bolt pattern is an odd one and pretty much requires porsche wheels. you're going to find that you need some pretty big offsets, meaning upwards of 50mm to fit most wheels to your super. my 17x7" et55 205/40/17 fronts are what's recommended for the front, but my 17x8.5" et50 245/40/17 rears will require wider rear fenders. there aren't a ton of bugs with 18" wheels, mostly because it's a pain in the butt to fit them under stock fenders.
you should read lanner's site about the porsche conversion:
http://www.vdubengineering.com/techn...onversions.htm
some people say their main allure is being able to say they're porsche parts, but the main allure for me was that they're cheap, good quality, and i can buy parts for them just about anywhere. most aftermarket disc brake setups are just as good, but you can't just pull them off a junk car. there are other parts requirements, but my whole setup wound up being a couple of hundred dollars less than regular 4-wheel disc setups, and mine are all larger and vented.
there's a whole lot of cool crap out there to learn about like subaru swaps, porsche transmissions, bmw power window conversions, rear coilover conversions, etc. but you sometimes have to dig to find it.