Connect rockford fosgate amplifier & speaker together

Assuming your P3 has a single voice coil (it will have only one place to plug your wires into) you will be running this in a bridged mode. You will take the left (+) coming off the amp and plug it into the (+) on the P3. Then take the right (+) from the amp and plug it into the (-) on the P3. This will make your amp push 500 watts to your sub. Now on the amp make sure your adjustments are as follows: Signal input switch is set to unbalanced for RCA input. Left Phase switch is set to 0. Right phase switch is set to 180. your X-card should be set to low pass. And adjust the gain for both R and L equally so it has equal power from both channels.