I have a Musarri Slip-on, and I love it. It comes with a silencer that I removed pretty much instantly and it's nice and loud, but not obnoxious.
It's quite cheap but from when I handled it during the install, it seems sturdy and looks great on the bike (my opinion).
http://www.xtremperformance.com/prod...bon-fiber.html
I got mine off ebay, but there's another link if you want to check it out.