From what I can tell, there was the
Sunfire Junior which utilized a 7" driver + 7" passive radiator, and a
Super Junior which bumped it up to an 8" driver plus 8" passive. Both were fed by a 1,500W RMS amp, and extremely compact.
Are they worth a spit? Depends. If you require the ultra-compact size...maybe. Even then, I'd be leery of the amp replacement costs. If you can accommodate a larger subwoofer, I know Hsu still notes that one reviewer found that their entry level STF-1 ($309+shipping) compared favorably with the Super Junior. Such small size practically dictates abysmal deep bass performance unfortunately. For ~$900, I'd look to something like a pair of SVS PB-1000's ($949 shipped). If you're willing to do a single sub at $900 and consider another such sub later, that opens things up quite a bit.