Abe, I am pretty sure Extreme and Exedy are the same thing - the $2,500 twin plate clutch I bought from Brenton at Adelaide Clutch for my S15 had BOTH brands written on the box.
Buy a heavily clamped (like 1,100kg - and you will need it with your power level) organic single plate clutch and you will be set. It will only last 40,000-50,000km, but they are relatively cheap ($1,000ish) and are pleasant to drive with. And if you find the pedal feel too heavy for you, you can modify the spring setup at the top of your clutch pedal assembly to make it more to your liking.
DO NOT under any circumstances get a twin or triple plate - they are almost always absolute cops to drive, and you will end up hating your car - I certainly did with the S15 - biggest mistake I ever made and I blew the twin plate in under 15,000km (did include many drag days though). I know some people have had joy with twin plates, but for 99.9% street driving and for any sort of daily driving forget it.