I would just like to thank annunaki, and everyone else who has posted such great informative replies on this thread. In this thread alone I think I've learned more about subwoofer design considerations and what factors truly impact a sub's performance than anywhere else I've been on the web. I'm no speaker builder by any means, but do understand engineering terms and can follow most of what's being said (at least once I learn the terminology and what they mean).
And now, at least - should I ever be bored and decide I want to just up and construct my own subwoofer, I know exactly who on this forum to target now.