I just put a WRX muffler on my RS. 125 install + 80 for the muffler/axleback. I got a 2.25" catback pipe installed w/ it.
It sounds really good. Very bassy. No droning, and its not *that* loud. Its definitely louder than stock though. Car sounds burbly and meaner now.
Also it does this thing.. I'm not sure why.. but at lower rpm (1.5-2k) it flutters when revs drop.. it sounds exactly like a wastegate or something..
Performance is good and its not annoying loud. I had a reallllly loud exhaust on my last car so i went the quiet route this time.