Magnaflows are good, and Dr. Gas has a good rep; however, Pypes muffs sound equally badass at WOT and are very subtle in regular driving, and they have a complete exhaust setup with off-road X and Violator cat-back (with stainless tails) for around $450 (price was ultra-cheap at their WFC9 display). Depends on whether or not you want/need the stainless steel materials for longevity and/or bling factor.
Jeez, I'm starting to sound like a sales rep for Pypes, lately...