Hertz DS 25.3 Dieci Series 10" 4-ohm component subwoofer at Crutchfield
Amazon.com: DS18 SLC10S Car Subwoofer Audio Speaker - 10" in. Paper Glass Fiber Cone, Black Steel Basket, Single Voice Coil 4 Ohm Impedance, 440W MAX Power and Foam Surround for Vehicle Stereo