Cat-back exhausts are from the CC back, which means that pretty much what they do is make your car sound different. What I'd do is keep your stock exhaust and bring it to an exhaust shop after you buy one (or two) resonators and then get a muffler in the "silencer" category" as low sounding cars will draw less attention from cops and everyone with a loud exhaust is hated with a passion on the roads. Plus, after about a month or so, you'll hate having a loud exhaust, it sucks trust me.