If the disconnect on the control panel disconnects all power to the equipment the only disconnect you need ahead of the control panel is your protection and disconnection means.
example:
-You feed from a 400 amp fused disconnect
-Run wiring which is good for the 300 amps(minimum)
Now you have a disconnection means with protection ahead of the equipment and the equipment is disconnected at the panel, and all equipment that is run from the control panel is or should be protected by individual fusing and such (assuming the panel is biult to code)
