I have the previous line's AX500a. It's a great sub, although it doesn't like my room very much. I think that Axiom's subs are fine...they'll certainly outperform any big-box-store junk, although without *quite* as much value as the loudspeakers.

It's probably because Axiom's subs are designed with music in mind first, rather than the how-low-how-loud-can-you-make-it home theater market.