ooOOOOooohhhh... I see...

Clever. Thanks for posting that. I'll take a look at the Jasper as well and compare my options.
Haven't made any progress on the builds this week. My neglected yard, house and housemates, and Starcraft all got their turn.
I did bring one of the Tubas in for a little home theater test. As expected, I hadn't even gotten the back end of the cabinet out of the garage door before one of the cats crawled inside the horn mouth to sniff around. No pictures unfortunately, hands were full.

It won't be the last time.
I rigged up a little test setup with audio baluns and Ethernet cable, since the only space large enough to place the sub was on the other end of the room from the receiver. Using my plate amp (50W), I got more than enough sound from it during the obligatory THX / Dolby logo clips. Ironically, not all of them had low enough bass to really give it a run. Pixar's "Lifted" short did the trick, though.
It became abundantly clear that my Polk sub has been playing up into midbass territory. My mains (RTi-35s, if I remember correctly -- it's been a few years since I've looked) sounded completely lifeless. I've been feeling the urge to replace them for a while now anyway. They lack definition, punch, and other words.
The Tuba sounded fantastic. I did not expect that -- it's a PA sub after all -- but really, this is the best sounding sub I've heard. And the tactile effects are truly palpable. Much more of a theater feeling than with the existing long-throw 10" vented box in the corner. So it looks like there will be a THT build in the near future...
After all the setup and testing, I watched what must be the only movie with
nothing but dialog for the entire duration. Not a single scene with any LF output. Not even in the DVD menu. I'm pretty sure my amp turned itself off fifteen minutes in and never turned on again. *sigh* Oh well... It was fun while it lasted.