Max power consumption is at 374W.



Yes. But your calculations seem to be implying that a 750W PSU operating at 80% efficiency can only handle 600W of DC load. No matter what the efficiency is a 750W power supply should be able to handle 750W DC. Unless it sucks. Or can handle a lot more, such as how the Corsair RM650x can handle 807W while keeping voltages stable and such before shutting off from overpower protection.