Gotta agree with Dr. House here; a subwoofer is a system to produce certain frequencies, and there are technical and budgetary design decisions to be made throughout the process. It's the end result that matters, not the inclusion of a certain chip.
I should think that ANY useful subwoofer DSP would necessarily be very closely integrated with a specific driver (and enclosure, and amp...). I like JC's observation about software - even if you're using the same DSP chip, you'd need different DSP algorithms for each change in the other variables.
It kind of reminds me of the great Audyssey debate. Sure, equalizing your speakers to suit your room seems like a good idea, but - in practice - many folks feel it does more harm than good. Something does not become inherently ennobled (or "better") because a new technology has been applied to it; either the technology itself or its specific implementation could render the resulting human experience unsatisfactory.
bibere usque ad hilaritatem