I also have the FRPP GTA axel backs that come standard on the Shelby. I love them. The car is my daily driver and I did not want to go too aggressive, but wanted more burble. Definitely worth it to me. The C&L intake added a bit of pop to it as well. No drone either, just nice American V8 modern muscle sound, plus the large tips look pretty sweet. I think that all baffled mufflers will sound pretty close to each other, just slight differences under WOT. The big difference will be the SLP loud mouths or any straight through glasspack "muffler."
Check out Ninosport.com as they have most of the mufflers with sound clips.