Newegg has Kicker 07C12-4 12" 300W Comp Series Car Subwoofer for $48 each with free shipping.
Specs:
* Size (Inch, Cm): 12, 30.5
* Impedance (Ohms): 4
* Max Rec Amplifier Power (Watt peak/RMS): 300/150
* Sensitivity (dB 1 watt/1 m): 89.1
* Frequency response (Hz): 27-500
* Mounting depth (Inch, Cm): 5-13/16, 14.8
* Mounting cut-out square (Inch, Cm): 11-1/8, 28.3
* Min Rec sealed box volume (Cu, Ft, Liters): 1.25, 35.4
* Max Rec sealed box volume (Cu, Ft, Liters): 3.5, 99.1
* Min Rec vented box volume (Cu, Ft, Liters): 1.75, 49.6
* Max Rec vented box volume (Cu, Ft, Liters): 2.25, 63.7
Newegg.com - Kicker 07C12-4 12" 300W Comp Series Car Subwoofer
Kicker 07C12-4 12" 300W Comp Series Car Subwoofer $48 + FS 
