Hrmm, i cant really say on a WRX, since i dont own one, but i know in a stock S4 from a 40mph a stock RSX Type-S was a cakewalk for me. Granted i do have a bit better topend then a rex, but i still dont think stock for stock it should of been an issue for you to take him. WRX are damn near an even match for my S4, so i think you would of been ok.
We also have to consider the driver factor, 3 or 4/10's of a second in a shift can make the difference.
I also have a funny story where a turbo'd RSX in my area (i later found out dyno's a little over 300 wheel) completely owned my **** from a 50mph roll. I mean it was bad, by the time we hit 80 he was approx 3 cars in front of me.