ditch the catback, keep the rest get a GOOD set of mufflers. I can't recommend anything since All I've had has been the HKS old-school catback, the one you have NOW and the RB catback. A few of the guys here can recommend something they use though.
I hear these magnaflows reduce decibel levels too:
http://www.magnaflow.com/02product/02race.asp
DUnno how much though.