if you still want a BOV for the noise, you can get a Greddy Type S kit for the WRX that recirculates the air back into your intake.

As far as intakes on the WRX i'm running a perrin intake and a perrin turbo inlet with no problems.

There isn't really alot of originality with a WRX, it usually goes exhaust, UTEC, bigger intercooler and a turbo upgrade(usually something from the IHI series).

Depends on how far you want to take your modifications i suppose.