I'm making about 290 whp on a dyno dynameter (XS Engineering).
I would say go with an evoIII 16g turbo, walbro fuel pump and modified stock injectors (if you have a tuner near you familiar with Subaru's they should know how to properly do this). Also suggest a bigger intercooler, catless up pipe & downpipe.
Then your tuner can tune your ECU with one software or another to make sure it runs at optimum.
The readings you get will depend on your car and the dyno, but that should put you there.