Ok well your first thing is to stop saying 450hp but I want 360whp. No one dyno's these motors so trying to figure out drivetrain lose is a joke. I have 409whp but don't go around saying its like 600hp.
Next where you live would be a good second so we can tell you if there is a good known tuner to contact. I have 3 in mind but I am in the northeast.
If E85 is attainable then get a protune on E85. Combine that with a full exhaust an bam you should be pretty close to your goal!
If not E85 then a really nice water/meth system then couple that with a full exhaust and Bam you should be close to your goal!
Otherwise go with a 18g turbo, turbo inlet, full exhaust, fuel pump and injectors with a protune.
STi's out of the box after a protune comes pretty darn close to what you want. You could just get a tune an see what it makes then go from there. You might find that is plenty and that's where you want to stop.
05 WRX Wagon - 409 AWHP / 334 WTQ Wicked Matt Tuned