Monoprice released two tower style subwoofers, the Monolith M-210 dual 10-inch subwoofer & M-212 dual 12-inch subwoofer. Both are THX Ultra Certified up to 3,000sf rooms. Big Bass, on the cheap.
Those looking to beef up the bass in their AV speaker system on a tight budget would do well to try the Fluance's new DB12 subwoofer. This dual ported $300 12" sub looks to be a great buy at $300.