Go with the Vance & Hines. They give the Sporty's a true Harley sound. If you don't get those, get a set of Cycle Shacks, best bang for the buck, hands down. Whatever you do, don't spend top dollar just for mufflers.
I ran my 883 without mufflers and the performance was off and it sounded like $^%#. It wasn't loud, just tinny. Supertrapp does best for performance but you need to run those dirt track pipes. I ran SE slip ons for $200/
I bought a set of Hooker headers and put them on last summer. They were extremely loud (so much so that the rest of my riding buddies made me run in the back). It was actually a little obnoxious. I just bought a set of chrome V & H shortshots from a guy here in Dallas for $300 with a fuelpak. Now they sound like a real Harley, not a hot rod. Not quite as loud, but the sound is a hell of a lot better.