You can also hop on youtube, get an idea what sounds nice to you. There is a few options like Magnaflow, Borla, custom Trubendz(variety of sizes and mufflers), and even the FSwerks stealth/race setups mentioned by Felix. If you do get an orp, you'll need some form of resonater or your ears will bleed from the rasp/drone.
If you want the best sounding exhaust, Borla is the way to go. You won't get much of a horsepower gain but you won't be able to stop grinning every time it pops and crackles on downshifts.
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