In the long run the 2.5 would be better. Is this goin to be a daily driver or straight track car? There are a ton of people making 300WHP on stock block 2.0 as well as 2.5. the STi block will make that 300 easy with turbo, tune, and fuel supply. Check out Unabomber's Manifesto has a ton of info and will prob answer your questions alot faster then waiting on a response. Even though it says no noob bashing people still will or just make smart unhelpful commnets.