Answers
To answer your questions-
Yes, it hits hard. Probably a lot harder than I need it to. It is built to JL specs (at least pretty darn close with the curves and all). I still need to do some more Dynamat in the back door and possibly another layer on the sides.
As for it being removable, with some work yes. Didn't want it to be too easy to walk away with. The box weighs about 200 lbs so its not like I'm gonna be moving it too much. I put the amp and cap on the side so I still had some room in the back. The box only takes about 15 inches so it's not too bad. I'm thinking about making some sort of barrier that I could easily put in front of it so I can load crap in there without worrying about messing up the box.