I don't think too many people are familiar with the Dawg Crusher. The Submersive is supposed to be a great sub, and there is at least one guy I know who upgraded from dual F112s to dual Seatons, and he really liked the move, though I'm not sure what he is on now. They are a lot bigger though, so you know, as in long. I think I remember seeing multiples of these subs in a high end dedicated, where they were set lengthwise against the front wall, if you have the space to do that.
Regarding the Bossobass stuff, I thought* I read that his designs might be of an inefficient, if not most inefficient design. However, it's always interesting to read his posts at AVS, as he knows a ton. I guess all I'm saying is that you might need mega amps for your listening habits with those. I might be 100% wrong, but I thought* I read that, so double check on that.
I vote for hiring Warp to build you LMS cabinets. Since they can handle so much power, get some monster amp(s).
Or the IB route too. If there isn't attic space, you can use space under the floor (if there is any). You can have like a box sticking out, like a large cube, and have drivers on all of its sides, for instance.
