in my honest opinion, exhausts that have 3 inch tubing etc. are a waste of money. i drive a modded b18b1 in my civic (DC 4-2-1 headers, high flow cat and OFF-BRAND midas exhaust, nice and quiet, the civic is pushing 14.5 in 1/4. i honestly think that a huge muffler that makes that obnoxious noise is not worth the money. the exhaust tip on the civic is around 2 inch's in diameter. dont spend too much on the muffler, get a good DC header and high flow cat (may have issues with the O2 sensor) and just get some midas exhaust.

Im willing to do a dyno with anyone in tucson AZ to try to prove my point, that your exhaust (catback) wont improve the numbers the civic is pushing compared to my cheap midas exhaust. and ill even do the work, just bring your cat back!