Price drop! Monoprice has the Monolith by Monoprice Dual 15" THX Certified Ultra 2000W Powered Subwoofer (M-215) for $1525 - 15% off with coupon code MARCH15 in cart = $1296 with free shipping. Produces bass under 16Hz, has Class D amplifier modules HDF cabinet, floating MDF grill, and a slotted port with foam plug.