Flowmaster Force II catback, Has 3 chamber (50 series) flowmasters. They are unbelievably mild at idle/part throttle. Scream at WOT, but still quieter than even a Super 40.
With stock mufflers on, I had enough interior noise that you had to raise your voice a good bit to talk in the car at cruise or around town, with the Force II's you can carry on a normal conversation in the car with the windows up.
Buddy of mine had a Super Turbo catback on his, and it sounded absolutely stock, just a tad deeper.