I got my 2007 Subaru Impreza 2.5i last month for only 3800. Sadly, non turbo. I'm trying to look into doing headers and a exhaust but no luck. 2.5i parts are hard to come across. and i hear the piping length and flanges are a in a different position by a few inches.
i read axlebacks options are:
1. Aftermarket RS axleback, but rotate flange to fit.
2. Stock WRX or STi axleback, which will bolt directly on.
3. Get a shop to fabricate a custom axleback.
catback
1. Aftermarket RS catback, modify flange to fit.
2. Stock WRX or STi catback, extend midpipe to fit.
3. Get a shop to fabricate a custom catback.

I've been looking at HKS Hi-power and Invidia N1 due to the look of the titanium look.

 

On my son's TS, we picked up a used SPT catback and modified his stock midpipe to bolt up so you don't modify the one that comes with it (or you will not easily be able to sell it). Since it doesn't make much difference on an N/A besides sound and looks, I wouldn't be looking to go with an expensive one.

 

Yeah im looking for a louder sound and look.. Currently it has a 06 axelback wrx exhaust with a valve inside the muffler so it sounds like a turbo but i don't like the sound of it anymore.