I drive a "mild" RS-T and everything said in this the thread is the truth when it comes to whooping WRX's.
My turbo runs 3 psi in 1st and 2nd gear, then 4.3 psi in 3rd, 4th, and 5th gears.
Running a custom turbo setup utilizing a Legacy RHB5 turbo, my car beat a stock WRX to 60 by two car lengths. Off the line it wasn't even funny, I friggin DESTROYED him. My car makes full boost at around 2200-2300 RPM as compared to the laggy and torqueless EJ20. I didn't even launch hard. He caught up to about a car length behind when he hit 2nd gear, but when I hit 50 mph and shifted to third I had him quite easily. Remember, a REX with stock gearing will get to 63-65 MPH in 2nd gear.
As I see it, he was BEGINNING running out of his power band at 50 MPH, and this is when mine was over, so I shifted to third and got my torque back. Thats where you get em'. Higher redline=not always a good thing.
Bottom line, you can't beat lots of torque and quick spooling turbo's.