Alpine SWR-10D4 Type-R 10" Subwoofer with Dual 4-ohm Voice Coils
I got two of these and put them in a custom box I made, response times are awesome, they hit really low and high, and at 8ohms per sub (about 600 watts per sub), they rattle your insides, and you can hear them inside gas stations, restaurants, houses, etc.