The sound of a WRX boxer was very nice. At idle it had a nice muted burble but then it screamed with the turbo at 6000rpm's gobbling up air. I had the 2.0L but I presume the 2.5L sounds even more powerful.
Are you
sure you want a 6.9 as a project car.
The exhaust note is sweet though. Sets of car alarms when you blip the throttle off idle.