I have the SLP "Loudmouth" on my '04 and it lives up to it's name. I'll never be able to sneak up on someone, or to sneak away for that matter
My Loudmouth has a drone in the cockpit at about 2000 RPM (give or take). It took some getting used to, and some folks may never adapt. I love the sound, and the gurgle during down-shifting. But that's just me. I'm sure a lot of folks wouldn't be happy. I get a lot of compliments from people on the street though. FYI: A friend has SLP's "Powerflow" with the larger diameter mufflers and it is considerably quieter than mine.
See if you can find a couple folks in your area to let you hear some cat-backs in person. That's the only way to be sure what you're getting.