6.5" Subwoofer Dual 4 Ohm 500 Watts Max Car Audio Sub Audiopipe TXX-BDC4-6 - Walmart.com
MMA124- 12" 500 Watts RMS Dual 4 Ohm Subwoofer
Amazon.com: Pyramid 12 Inch Car Subwoofer Speaker - 500 Watt High Powered Car Audio Sound Component Speaker System w/ 1.5 Inch Kapton Bobbin Voice Coil, 8 Ohm, 25 oz Magnet, Cloth Edge