look into the pypes super system. i have it and it sounds like a beast, period. its loud but has a nice defined tone to it, not one that falls apart.

http://www.youtube.com/watch?v=8Bhiz6VgLKI
http://www.youtube.com/watch?v=jHKgapzvwTQ

and this is when the long tube headers are added, the revs sounds werid on camera but when he gets on it you can hear how intimidating it turns the WOT tone into

http://www.youtube.com/watch?v=AEht-_-Jkl0

 

I personally love the way Borla ATAK mufflers sound on the 5.0. They really sound phenomenal to me. A great mix of hardcore muscle car growl during WOT and not-too-loud cruising rumble. I also love the afterburn "popping" sounds when you let off the throttle.