I run a default Turbo muffler on the back of my SJ-410, sounds great and a perfect match for the engine. When I get on the gas you can hear it a bit but for the most part it is completely silent. Under the Tracker I have a Flowmaster, nice and quite for cruising but you can get a bit of noise when you wrap the engine up. I thought it sounded great until I got behind BRD HNTR's V6 with the dual pipes, but there isn't much of a comparison there.
One issue with running the muffler that far back is that you have to make sure you have room to run it next to the gas tank. On my SJ with springs under it I had the pipe straight back, ran a 45 degree angle up, have the muffler, then another 45 degree angle that put's it over the axle, then straight out the back.
Here is a good shot of an exhaust from a Samurai that is well put together -