jc whitney has a good muffler that can be used as a resonator. they come with a 4 or 5 inch cylinderical case and works real good at quieting the exhaust. my boy put one in his civic with a hks muffler and no cat. at first it was super loud. he put the resonator/muffler where the cat use to be. now it sounds as quiet as it did when it had a cat. i also had one on my mr2 before i switched to the thrush turbo muffler. heres the jc whitney link.
http://www.jcwhitney.com/product.jhtml?CATID=5446&BQ=jcw2 
