If I were buying one, I would go with the SVS PB-1000. I like really deep bass, and it is the only one listed that is really capable of 20 Hz performance. Add to that the best warranty, and likely the best customer service (or at least, among the best), and it seems like the obvious choice to me. Of course, for someone who wants loud more than deep, another choice might be better, but for me, that would be the one if I were buying a $500 subwoofer.