Thanks for the responses. It's not going to win any awards, but it does seem like a possible "flank steak" of car audio. Dirt cheap, and with some added work, could still be pretty tasty.
This (or a similar sub) may be a fun SB1 project for the summer. With one 12 and enough power to blow it... see how many dBs it can take before the magic smoke fairy comes to visit.
note: the sensitivity isn't really 96 (as advertised on the box) Sonic Electronix has 89 dB/w-m which is more reasonable.