I'm running a 40 series Delta Flow. It has a nice sound to it on the outside, although it resonates some on the inside still, but not so bad that I can't stand it. As for buying the full catback system, I would recommend just buying a muffler and taking it to an exhaust shop and have them take care of it. I would imagine that you would save some money that way, and get the exhaust the way you want it, rather than just a cookie cutter type setup.