Me personally, have tried the cat-back performance exhaust from magnaflow. It gave a subtle deeper rumble, but nothing like a straight piped loud annoying fart can honda. I'd say magnaflow is the best if you buy the full cat back, but then again I havent heard what else is out there!
I know there is ddm works, zzperformance and you can get custom welded ones. But I would like to know your guy's opinions too!