i may be wrong but i believe the torque more than the power is what eats boxes,hence 2.5's having more problems when tuned due to their ample torque
ask a proffesional ciaran but id budget for a ppg kit or 6 speed at some point,if your upping the power to high 300's id also suggest you may need uprated fuel rails and fuel pressure regulator.
definitely you want uprated calipers though,prodrive alcons,newage brembo's or ksports id suggest
and dont forget hawian shirts add at least 80hp