MTX RTS8-44 Road Thunder Series 8" subwoofer with dual 4-ohm voice coils at Crutchfield
Kenwood Excelon KFC-XW800F Shallow-mount 8" 4-ohm subwoofer at Crutchfield
Amazon.com: MB Quart DS1-204 Discus Shallow Mount Subwoofer (Black) – 8 Inch Subwoofer, 400 Watt, Car Audio, 2 Inch Voice Coils, UV Rubber Surround, Best in Sealed Enclosures : Electronics