Original box was 2 ft ^3 tuned to 34 hz and it sounded great in my Jetta. I haven't put it in the Fj yet. I am waiting on a fiberglass box to replace the factory subwoofer. The new box will be sealed at 1.2 ft ^3 before displacement so I'm going to add some poly to try to get it up around 1.5. I will let you know how it sounds in the sealed enclosure. I could not be happier with it. I had to opportunity to sell it a couple different times but couldn't pull the trigger.
I plan on adding deadener slowly. Probably start with the front doors and rear hatch. I might go ahead and do under the front seats while I have them out installing my amps.
I haven't had it offroad yet, can't wait for spring. I'm sure it would go find in the snow but I don't want to chance getting stuck in the woods until I know what it can do. It goes great in the snow and have only had to use 4wd a couple times. I have never had to use low or the lockers. It gets lifted in May, 3" rough country suspension lift.