My current 500" street Duster has an H-pipe, 3" system, Super turbo mufflers, and 2.5" tailpipes. It's almost too quiet, I'm gonna try some cheap stainless Jones straight-through mufflers soon. I do have electric cutouts on it though.
I tried Borla XS street mufflers on this car and they weren't much quieter than open headers.

By the way, I also tried Summit 3" turbo mufflers when I first got this car running 2 years ago and the cases blew apart after only 2 months. Summit gave me my money back and said they've had a lot of those returned damaged.