Newegg offers the Polk Audio 300-watt 12" Powered Subwoofer in Black, model no. PSW505, for $169 with free shipping. (Amazon charges the same.) That's the lowest total price we could find by $98, although we saw it for $9 less last November. It features a frequency response of 23Hz to 160Hz, magnetic shielding, volume control, an automatic on/off switch, phase switch, and adjustable crossover.