I have used Flowmaster Muffler 40 series since their inception. My kids slept through all the power shifts and passing gear downshifts of slushboxes just fine. But my kids were raised around hot rods and drag cars from their birth.
I don't car what anybody says... the Flowmaster 40 series pioneered the sound of power for a street/strip rig... Nothing sounds meaner... but that's just me.
Gary