Flowmaster makes several series of muffler. The new 40 series is supposed to be a very nice sounding muffler. I haven't heard a set myself, but the guy at the shop that did my system said they had a nice Mustang rumble. The 50 series I'm told is LOUD!! So if you like your neighbors, you may not want them!
I went with the DynoMax Super Turbos. I have had them on 3 of my cars over the years, and I really love the sound....not to mention they flow like an SOB.

(Again using the Mustang as the benchmark, that's about what I sound like at idle, with a very nice rumble as I accelerate.)
Ray