With exhausts there is a bit of a difference. Do you want it more for performance or more for sound? Performance wise, you want a straight through design, like magnaflow, borla, dynomax bullets, ect. Real aggressive exhasts tend to be chambered like Flowmasters, Cherry bomb's chambered ones, Flowpro, ect. Chambered mufflers will usually be loudest, but they hurt performance to some extent because they don't flow as well as a straight through design. I would try to find a mix that suits for needs best. In the end, it comes down to what Blue says, exhausts are mostly for sound, but there will be a bit of difference just to make you aware
A Gryphon tuner is one of my plans for next summer, seems like one of the best mods you can do.