J90RDN

Had my 2006 2.5 STi for a month now - totally standard and sounds a bit tame. I heard an RB320 tonight and sounded sooooo much better than my 2.5. I assume these have the PPP package as standard. I was wondering if I could just get away with fitting the prodrive back box to get a better sound? I don't want to go too much louder or get an aftermarket exhaust, as I do 120 miles per day and don't want it too loud, and will probably be selling the car in a month or 2. Just want the proper scooby experience before I sell up, and somethings thats easy enought to swap straight back.

If the prodrive back box was from a 2.0 (say 2004 or 2005) would it still fit the 2.5 OK?

Thanks