As far as which one sounds best your really gonna have to decide that for yourself.. Most people seem to go w roush... I personally am not a fan.. I have flow master hushpower mufflers.. They sound great BUT they have the dreaded drone.. If I ever switch mine then I'm goin w gt500s.. If you want to compare there is a vid on YouTube called roush vs. hushpower vs. gt500.. It's a great comparison vid..
Bama 93 race tune, bbk o/r xpipe, gt500 axle backs, frpp k-springs, steeda rear lca's, 3d carbon 3d500 wing, boss/cs front fascia w boss brake cooling kit, plenty more...