I've done similar power mods to John to the GB270 along with whiteline rear ARB, ALK and fast road geometry settings, the car is running 345bhp/380lb/ft and is superb to use as a daily driver and for fun, but if I was doing it all over again i would definatley go for a STI.
I'm now thinking of more power and trackdays, so brakes, gearbox and forged bottom end are coming into my thoughts
As a road car the WRX with the stage 2 mods is great to drive, but it depends what you want from your car, I made the decision to go for the WRX(GB270), but with hindsight I should have gone for the STI.