It all depends on how fast you are and how you use your brakes... there are people at HPDE that have been doing it for a while that don't use the brake enough to smoke light duty pads and stock rotors - even on a WRX.
This year I upgraded my car to the Stoptech kit and drove around on the street with the Axis pads in it. Not bad. But... for the track I ordered a set of Cobalt VR spec pads for it. Let me just tell you that the pads are unreal. They're very easy to modulate because when they heat up there's so much grip on the rotors you don't have to try to shove the pedal through the floor to make the car stop. I wouldn't run them on the street all the time but they were totally fine to and from the track. (www.cobaltfriction.com
I think a lot of people try to go with an all-purpose pad and I've done that before. Works okay on the street and on the track to an extent. Pads aren't that expensive and the race pads last forever. Personally, I'll never use anything less than a full race pad on the track now that I've felt the capability. I don't know what your skill level is on the track, but if you brake hard enough in EVERY braking zone to keep heat in the pads try the VR spec if you can get them for your car, you really won't be disappointed.
I looked on the website and saw that they don't have a listing for the STi but that caliper is pretty common. Andie is the guy in charge there and really knows his stuff.