if u want it to be a lil loud,my boy has Apexi N1 on civic...and that definatley did the trick!

 

u want loud?just do 2.25 from the cat back no resonator or muffler, or u can leave the resonator in. but it will be a nice deep sound and sound high pitched when u hit vtec

 

look up greddy, apexi, megan racing, tsudo (i have this one), magnaflow.......just to name a few. these are of course more about performance than loud. my tsudo is a bit on the loud side but pretty deep too. and i got a deal on it too. (i didn't have 300+ to spend on an exhaust)