Think of it this way: given your current circumstances, how big of an upgrade will the FTWs loaded into the 8cf flat pack represent over the UXL DO box it will replace? I'm guessing you aren't making the UXLs beg for mercy, so the main benefit beyond bragging rights is an incremental gain in efficiency. Doesn't exactly seem worth the effort, but that's just MHO. The big box, while a giant PITA, would turn that marginal gain into a reasonably large step up. Still, I'd agree that I'm not sure it's really worth the effort/massive box in my living room.
Given the practical issues that you're facing (space, power, etc.), I'd think hard about simplifying your setup. Putting each FTW into a ~7cf cabinet, and selling or storing the LMS-U's and UXLs until you move seems like the most viable option. You won't sacrifice any output over your current setup and it wouldn't necessarily take up a lot more room. More to the point, with a single 15A/120V line, it's not like you're going to do justice to a pair of FTWs and a pair of LMS-U's anyway.