Amazon offers the Definitive Technology ProSub 1000 300-watt 10" Powered Subwoofer for $374 with free shipping. (Crutchfield has it for a buck more.) That's the lowest price we could find by $41. It features a frequency response of 18Hz to 150Hz, 300-watt RMS amplifier, and 10" woofer coupled to a 10" low bass radiator.