Blastin Bob can sell the entire replacement kit for a decent price. You would be able to install it yourself and save some cash or take to a local installer and have them do it for a 100 bucks. Just an idea.
I have the 6db resonator replacement kit that took me to a dual pipe system and love it. Of course your going to need the new muffler system and he offers this in kits as well. You can see the results on my web site under upgrades.
Their site is
http://shop.alliedmuffler.com
Or give Bob a shout at
BlastinBob@aol.com