Amazon.com: Alphasonik AS8DF 8 inch 600 Watts 4-Ohm Down Fire Shallow Mount Flat Enclosed Sub woofer for Tight Spaces in Cars and Trucks, Slim Thin Loaded Subwoofer Air Tight Sealed Bass Enclosure :
Amazon.com: KICKER TRTP 10-inch (25cm) Thin Down Firing Subwoofer and Passive Radiator Enclosure, 2-Ohm, RoHS Compliant : Electronics