Polk Audio DXi104 DVC 10" Dual-Voice-Coil 8-Ohm Subwoofer for $29.99 shipped.  Here is a screenshot for your reference. It handles up to 540 watts peak output at 4 ohms, 86dB sensitivity, 28Hz to 200kHz frequency response, 8-ohm impedance, high-temperature copper voice coil and polyamide former, and polymer woofer cone.