About smaller systems suitable for the LAB12 woofer, Mike E has built some smaller horns, and they modeled quite nicely from 40Hz up. The LABhorn was designed for 30Hz, I believe, and so Mike's horn trades 10Hz on the low end for size.

Another thing I think is pretty attractive is to use them in a 2ft3 to 6ft3 cabinet tuned to 22Hz. That will provide maximum output of about 115dB at full power, which is not too bad for home use. The small size is nice too.

I understand that lots of people using the LABhorns for home theater are EQ'ing them below 30Hz. Down where the horn unloads, the system becomes a direct radiator so that makes sense. Removing the horn makes this unneccesary, but the obvious reason is that now the entire subwoofer range requires more power.