this is what i did for my 2008 impreza 2.5i base model

i got ebc slotted rotors and ebc greenstuff pads for a wrx ( the 2.5i ones are 10.9 and the wrx ones are 11.2 )so all you have to is buy either a 2008 and up brake caliper brakets which cost about 80 a piece new or used brakes like i did the caliper on the base model wrx is the same as the 2.5i but the braket fits the larger rotor

anyways i did this upgrade and much better then the stock brakes better stopping power all the way around