skunk2! *snicker*
I have a skunk2 cat-back. Very nice exhaust. It is rather loud BUT with just a slight amount of throttle (like the amount needed to maintain freeway or surface street speed) it becomes almost silent. I figure it must have been tuned that way. I don't mind when it is loud though because I like the way it sounds -- very deep and throaty, not like your generic civic fartcan noise which I think sounds horrible.
The sound my car makes full throttle at 6k+ RPMS is wonderful
P.S. Some people say an exhaust like that will get attention from the police. I have had the exhaust on for 6 months and haven't been pulled over. It's really no louder than a truck with a flowmaster. If you get pulled over for your exhaust then the cop was just in a bad mood or felt like being a dick