Kenwood KFC-W3016PS Performance Series 12" 4-ohm component subwoofer at Crutchfield
Amazon.com: AUDIOTEK Pair of Car Vehicle Subwoofer Audio Speaker - 10 Inch Competition Pressed Paper Cone, 4 Ohm, Advanced Air, 1000W Power for Stereo Sound System K710 (2 Subwoofers) w/Wire PK12 Bundle : Electronics