If you're considering Subaru engines I recommend going with the JDM EJ207 with the twinscroll turbo. I have enough friends that have done subaru to subaru swaps and that is the preffered motor. It's a two liter that's fairly reliable and pulls like hell!
It also doesn't suffer from the ring land issues that the EJ25's do. Just something to take into consideration if you start modifying it. I had a friend with a 2009 STI hatch (had just about every single bolt on) and it grenaded. After almost two years the car is back on the road now making 430AWHP lol.. It was an interesting build to say the least and I'm pretty sure I'm poisoned by the amount of coolant I got in my mouth when he undid his rad hose LOL.