No need aftermarket the wrx tmic is same as the xt. Never go with a bov always stick with a recirculating bpv for a subaru. And the stock plastic one will only take about 20psi. And won't gain much from intake besides being able to hear the turbo more.OEM STi, haven't played with SH so I'm not sure what fits (stock WRX?). Basically, whatever is OEM with the takeoff turbo you use. They will work better than cheap Ebay stuff.
Key to longivity on Subarus is to keep it very simple. Find a good tuner, keep boost target around 14-15psi and enjoy the ride.
Aren't you guys on ACN91? A tune on 93 would surely yield more power.OP mentioned "safe" and "long run", 300whp on a VF52 is not safe, just throwing it out there. If you want 300whp, the proper way to get it is with at least an 18G and injectors. Not bashing, just giving a heads up. East Coast fuel may be better, or dynos read higher, around here 300whp on a VF turbo and pump gas is not possible safely.
Find a good tuner, explain them your goals and budget (be honest about both), listen to their advice.