question about subaru engine swapping

[gubble_bum]

soo... my dream 'domestic car' is obviously the 2004 impreza wrx sti, blue, gold rims, 6 speed manual/auto (prefer manual), big spoiler (not the smaller one), 300hp 300flbs torque, yeah.. i know like pretty much all the specs... but thats not exactly what i wanna talk about..

i was wondering if it would be possible to stick in a bigger engine then the stock one.. i was thinking along the lines of a turbocharged v6 engine. would a 3.8L be too big for the car? what kind of engines would be able to fit in it and what kind of work would be involved? (i.e. replacing transmission, etc)

i want to know this so i can do all this when i finally do get my impreza.. i love that car and i know its already pretty fast with a turbo 4cyl... but how would it do with a turbo v6 or even a supercharged v6? (like the pontiac gtp) any feedback is greatly sppreciated!!