They may end up being used for theater, but probably not very often. Primarily I'm just after pretty damn loud with low distortion. To date, the only subwoofer I've built that impressed me were the lab12 ths I built. Been building and chasing for about 20 years and I've mostly stuck to simple vented cabs, but the th is happier playing up at levels I find fun, so rather than build yet another vented cab that'll get me into the 120s sweating bullets, these are more likely to get me grinning. If I end up missing that bottom end, I'll start ordering 24s for next year's fun time.
Swapping the plug in and out was one of the things that caught my attention when I started looking at this. Do I want dubstep mode or metal mode? Hmmm...
You are correct though, I'm sure the output will far outpace what a single sealed 18 would do, even at 1 foot from mlp distance. I'll come up with something, eventually. If I even miss it.