least loud aftermarket exhaust.

[scoprire]

I've got a set of MIIV x-cone that aren't too loud, but better than stock.  If that isn't enough, you can always order a different size db killer to open them up a little.  For the X-cone, 25mm is stock, I got a set of 30mm from PJs that sounded really good, but isn't very friendly for my neighborhood.