Fill out your profile. Location, car, etc. Go to a subaru performance shop near you, and ask them this question. not a bunch of random people on the internet. Cuz I will tell you to do this:
STI 6 speed trans
build your 2.0 to handle the hp
the list goes on. It will cost you well over $15,000.
Or you could be more specific. tell us a hp number you want, and ur budget. Or jsut go talk to professionals.