[Dosturbos]

I'd throw a new charge pipe with diverter valve into the mix (along with Dp's, FMIC and CAI), if you're going to hit 400tq/400whp, without meth, you're going to need to be able to build and hold boost. If I did not buy my car with full exhaust already installed I would not spend extra dough on midpipes. Spend the cash on a good axleback and high-quality downpipes that fit right. The shitty ones vibrate and are too loud.
Also, you can have a custom map made for your AP. I know EFI Logics in CT does this or Bren Tuning in Worcester, MA can also do it. It's way better than an OTS map.
Also, Mistr135, this car isn't an STI or EVO. The car has Direct injection and a High pressure fuel pump, you don't need to dick around with any of that Deatschwerks crap to get better fueling. Also, the 135's ECU is far superior to that of a Subaru or EVO.
Speaking as a current WRX owner.
Also, once you buy a bimmer, you have no friends, everyone immediately thinks you're an asshole with too much money to spend.