I am currently running a 10" Kappa Perfect in a .6 cu foot sealed enclosure that I made for my last car. Fits well in the KJ, and I wired it up for easy removal. You won't get the really deep bass a 12" or 15" will get, but I think it's a great sub for all music types - rock and rap. I have a CRAP amp on it currently, and am running it off the stock radio (Line Level Converter used) so it really isn't hitting it's full potential.
For easy removal, I screwed a metal "u" hook to the back of the box. The box is tapered so it somewhat fits along the back of the rear seat. The hook grabs the anchor that's in the middle of each section of the back seat - I covered it in carpet so it doesn't rattle and scratch the hook. I then put velcro on the bottom of the box so it doesn't slide. So far this setup has held it firmly in place, even when offroad.
I threw a switch in the dash that cuts the remote wire - so, I can make sure the amp never powers up even if the radio is on whenever I want it to remain dead. I did this so that in about 10 seconds I can flip the switch to cut the amp off, pick up the box, and unplug the speaker wires. It's nice that in 10 seconds I can have my entire cargo area back to it's full size
