Axiom Home Page Forums General Discussion Home Theater Budget sub for M22s?

I've perused past postings on subwoofer recommendations with great interest. At this point, I'd like to narrow the focus a bit. I currently have a pair of M22s and a Denon AVR-1802 in a largish (459 sq ft, 3672 cu ft) room. I would like to add a sub. My goal is to achieve the best possible MUSICAL quality for my buck; movie sound effects are relatively less important.

So here's the question: What subwoofer would you old hands recommend for (US)$400 OR LESS? (P.S. I'm not much of a DIYer.) Thanks!