I brought a blueflame cat back system, which sounded not much louder than the standard exhaust but gave a much better sound and good turbo noise. you really need somebody else to drive the car away from you or past you so you can hear the noise for yourself, you cant really hear it from inside it sounds totally different. it wasnt loud at all with just the cat back but sounded good.
i have decatted it and put the downpipe on from blueflame also and it is much louder now. doesnt sound raspy and chavy though, it is alot louder than just a cat back but its more of a loud turbo noise and not doesnt sound like a subaru, i would like it a bit quieter i think though. but it might be worth it for the performance gain