We just sold our 2006 GT Mustang and purchased a 2008 Shelby GT 500 which we love every aspect of with the exception of the whimpy exhaust sound.  What would be the best exhausts to put on it that at least sound as good and throaty as the GT Mustang, but not so loud and obnoxious that you have to yell at each other when you are cruising (no drone)?  

I have the same complaint about my 07 GT500. You would think that the most powerful mustang ever produced would have a better exhaust note right out of the box wouldn't you?
I haven't made up my mind yet regarding which exhaust I'm going to go with but I'm leaning towards the FRPP 5GT's simply going on what others have said.