Best Buy: Pioneer Champion Series 12" Dual-Voice-Coil 8-Ohm Subwoofer Black TSW310D4
2) Pioneer Free Air Series Speakers TS-W25F Subwoofer | TRS Consignment Auction: Great deals on Automotive parts and accessories, Vinyl Machine Business set up, Griddle and more! | Equip-Bid
Pioneer TS-W303F 12" Free-air Subwoofer at Crutchfield
TS-SW3002S4 - 12" - 500w Max Power, Single 4Ω Voice Coil, Mica-reinforced IMPP woofer- Shallow-Mount Subwoofer | Pioneer Electronics USA