Here is a circuit Power Amplifier with output power of more than 600 Watt speakers with impedance of 4 Ohm. Power Amplifier circuit with high power uses n-channel MOSFETs 6 in the output stage alone is giving about 400Watt power. And to make more than 600Watt need to use 12 N-Channel MOSFETs. One of the construction sequence to produce more output power of 900W using 12 IRFP460 MOSFET. Here is a Power Amplifier Circuit Diagram, and the Power Supply is suited for this amplifier. I also include a PCB Layout Design for the power amplifier and its power supply, you can see below.