grats on your wrx
awd turbo's are completely different than a n/a fwd 4 cylinder.
you did a complete 180.
the potential of the wrx is very nice. I'd suggest grabbing a ecu reflash and a catless exhaust +mbc to start off, should make the wrx just a tad faster in a straight line than your gts was, and best part is if you shop around you can get it all for under 1500 or so!
another thing to remember in an awd car, they usually get heavy understeer at corner entries, and if you take any corner in at a reasonably fast speed you will hear tire squeel, its normal and dont panic and throttle off, it causes your line to go to hell.