by parts do you mean performance or aesthetics?

on the performance side, it was my understanding the legacy has a "de-tuned" ST-i EJ25(this might be the GT so someone please correct me if i'm wrong). If thats the case and it does actually use an ST-i ECU that just has less agressive setting i'd suggest getting the UTEC. That will allow him to get alot more agressive setting on the motor, free up the exhaust with a turbo-back system and it will feel like a completely different car

where ben at? he would know alot more than i would.