Just put on Banks cat back duals along with the BD manifold. I also run an AFE intake. The Banks is just slightly louder than stock, most noticable at low RPM. The was a noticable improvement in power along with a slight improvement in gas mileage. I went back and forth on either the Banks or MBRP (most popular in this site). I wasn't looking for an increase in sound. In the end, it came down to $$$. The Banks came with tips and a lifetime warranty for around $700. Everything was well packed and I had it installed in about 2 hours in my garage.
Katoom
05 LLY, AFE Magnum Stage 2, Banks Duals