I just bought a set of 2.25" Rush slip ons from another HDForums member. Put them on tonight and, WOW! what a difference. They sound great, although when I have the bike in the garage, it shakes the whole house (or so I am told by my wife and kids)
Jason32mn: THANK YOU so much for the tip to take off the bracket. That saved me an hour of profuse sweating and swearing. Once the bracket is off, you can twist the mufflers, which makes it a LOT easier to remove them.
BTW - my bike is a 2013 Wide Glide, so the catalytic converter is in the head pipe. I had e-mailed Rush and they recommended 2.25" instead of 2" due to the additional restriction and sound muffling from the catalytic converter. As far as I'm concerned, the sound is perfect. Not obnoxious at idle or low RPM, but you can hear it when you roll on the throttle. Very pleased with them so far.