best way to get a deep sounding exhaust is to have fairly large pipes.. 3" or 3 1/2"... and run them all the way to the back with the mufflers up front.. close to the manifolds.

http://www.jegs.com/p/Cherry+Bomb/769804/10002/-1/10265

glasspacks are cheap and have a nice deep sound at idle and low rpms
and sound pretty good if your gettin on it too.