It depends on what you consider a nice sound. I personally like a deep, mellow sound, so I like absorption type mufflers like Hooker Max Flow, Dynomax Ultra Flow, Magnaflow, Borla, etc. If you like the Flowmaster sound, there are different options for that.
A buddy of mine put some turbo mufflers on his Nova with a mild 383, that he bought at Midas. Those things sound awesome!! They are nice and quiet when cruising, but when you get in the peddal the are loud, and have an awesome tone!! Who would have thought a cheap generic muffler would sound so good?
Flame away but I love the way my 50 series flows sound with the x pipe and full tails. I know I am giving up et but they sound great. I dont like how they sound on a stock engine but on a hot street motor they still have the best sound IMO
My neighbors tell me they can "feel" my car over a block away before they can actually hear it pull up