So I initially had installed the 22" single in/dual out (SI/DO) exhaust on my 2010 TRX 4x4. This is the bolt on kit that converts the stock exhaust to dual exhaust. Just thought I would provide some feedback on this system.

22" muffler sound -
slightly meater tone over stock
When getting on it sounds good but not overly aggressive
seems like there is better throttle response over stock exhaust

But, I decided to swap out the 22" for the 18" magnaflow. I was looking for a slightly more aggressive note without getting a large amount of drone in the cab.

18" muffler sound -
meater tone over 22". At idle it is a deeper note.
When getting on it, the truck sounds healthy but mean. Love the sound of it as it rises through the rpms. Definitely lets you know that you've got a hemi with plenty of umph under the hood.
off the throttle I'm most impressed as it sounds very similar to the 22" and drone is not bad at all. There is more sound in the cab when MDS kicks in but nothing that would keep me from buying the 18"
Overall, the 18" for me is the way to go.

For anyone that is interested I do have the 22" magnaflow muffler for sale. It has about 5,000 miles on it and in excellent shape with no issues. The muffler hangers were removed for installation on the 18" by the local muffler shop. The muffler will need to be welded on as the local shop cut it off. But after seeing the local muffler shop install my 18" muffler in 20 minutes and needing to cut the old hangers off and add some additional pipe, this would be an easy work for any local shop. (it cost me $75 to install the 18") Anyone that is interested please PM me, as this exhaust won't do me any good sitting on the floor.