PC power supply is not a good solution. Why? Cause L3+ works continuously. Cause needs 9xPCIE.
Good 850W/230V computer power supply is 87% efficiency (80 plus GOLD), so only with Gold, Platinum Certificate. But power should be greater - do not use 90-100% power supply limit. However, good power supplies can handle it such as the Corsair CS850M, which has a continuous power of 850W for 12V line and peak power of up to 935W. But what if it has only 4 PCIE slots?
Better use power supplies for servers. So APW3++ from Bitmain will be ok.