I just installed an American Security BF6032 in my house. I originally wanted to put it in the closet. Even though it would fit dimensionally, I could not get it through the door, even after taking the door frame off. Anyway I ended up putting it in the hallway, instead. I guess it's a conversation piece now, lol.
It probably weighs 1000 lbs. or so, with what I have in it. There is about a 5' crawl space under my house in that area. Even though I think the floor would support it, I put two post jacks (on concrete pillars) centered under sections of 4x4 that spanned two floor joists. This is most likely over-kill, but I didn't want to take chances on the floor sagging in the future. The post jacks are available at Lowes for about $30. The jacks I bought adjusted to a max height of 4'7".
Spent a good part of the day installing it, fighting insulation, water pipes, putting the door frame back together and bolting it down through the floor. I'm quite happy it's done, but if I'd known it wouldn't fit in the closet, I would have ordered a bigger size.
Good luck