Unless you came from something faster than 0-60 in 6 before you should wait and enjoy the speed you have for about 6 months when you will think it is slow. Then put some money into it and make it faster. This way you have excitement that lasts a lot longer

I agree with the above, TBE then some sort of Engine Management. Cobb is great if you want good gains and are not going for anything to wild, a UTEC is good if you want to tune it or you can get a Perfect Power from rallitek for cheaper and that is more tunable than a cobb. Sway bars are probably going to be your best bang for your buck (although I am not sure about the sti). I recoment the IPD kit. It is $350 and comes with front and rear swaybars and solid metal enlinks. It save you like $70.
-Travis