Just got this exact same setup as well (roush axle-back exhaust w/ x-pipe) on my 15 gt convertible premium. When I first drove it away from the shop after installation, it sounded extremely loud and I was a bit worried. Not sure if I've just gotten used to it or what, but I actually LOVE the sound now. It's loud when you want it to be, and it's just quiet and waiting during the other times.
No regrets whatsoever. Definitely grabs the attention from everyone
Good luck!