Honestly based upon the RMS ratings of each of those subwoofers your best bet is to go with the 1 12 inch Kicker Solo Baric L7 which is rated for 750watts RMS at a 4 ohm load, the 12 inch Rockford Fosgate P1 subwoofers are only rated for 150watts at a 4 ohm load.
This tells me instantly that the 12 inch Kicker Solo Baric L7 will completely destroy even 4 of the 12 inch Rockford Fosgate P1 subwoofers.
Just make sure you purchase an amplifier which can handle a 4 ohm load (almost all can) and is rated to push out 750watts RMS at 4 ohms (If you go with the 12 inch Kicker Solo Baric L7)
