If you want to really fix up your ride, and put the hard work into it, go for the gsx, but if you want to buy a car that is fast as hell already go for the STI. Im not sure what the aftermarket support for the STI will be like, but starting from 300hp is a good start. The STI looks pretty good stock, except for the Hood
scoop, but with a kit it would look tight. My opinion go for the STI.