There is no 2006 Impreza RS.... Dont the Impreza 2.5i have weaker transmissions than WRX's?

Judging from your comments of just wanting to learn/tinker with your car, I really think you are in over your head... I was going to turbo my previous car (which will remain unamed, just know it was a lower end econo box) and quickly realized that it was a lost cause after looking at all the modifications you have to do... give up and buy a WRX

Theres always suspension mods... put that AWD to work, and hell you can squeeze a few extra horse with a CAI and exhaust...