If u have a problem with sound, then definatelty get a cat... Some exhausts also have a resonator on the mid pipe that also helps reduce noise, alot of cat back exhausts exclude it for performance reasons... But u can alwasy get a stock mid pipe with a resonator on it...

I like mine kinda quiet when crusing around, and when I get on it I want it to growl... It used too, but I recently accuired a hole in my resonator and it sounds horrible... I need to fix that... But I dont want mine loud for the simple fact around here cops are bad about noise...