I've got one chambers on my car right now, but they're dumps. Man they sound AWESOME IMO!!!! Also, I don't hear myself everywhere I go
I'd suggest an H-pipe, may not net that extra 2hp, but the sound you gain is MORE than worth it IMO.
Also, I didn't like Magnaflow mufflers or catback, just didn't sound good to me....
I'd go w/ Spintech, Flowmaster, Borla, Dynomax, or Mac (Mac sounds damn good when used w/ a Prochamber).
-Will