I had to order a new cat for my EX... I ordered a high-flow because the stock one is something like... 1100. I was told it really doesn't make much of a difference power wise...(not sure about sound) kinda just works better with an aftermarket exhaust. After I get the cat on.. Headers are probably going to be my next add on.. just to kinda complete the system.
Janna

Forgot to mention... there are laws that prohibit you from swapping a cat before something like... 60K miles...(unless it's missing.. busted.. etc) not sure how that's enforced tho.