Thought i'd update this, been a while
Stebel Nautilus An ear-splitting 139db four inches from the source, and a healthy 115db 2 meters away
sounds like this
http://www.youtube.com/watch?v=l8JsYLOIOX8&feature=related
2 1/2" downpipe and 200 cell cat fitted, then full 2 1/2" system...