Ok, is there any other good PSU to power 1 S3? Corsair VS650 is not good then as it has 2 8PINs on 1 cable?
I have a VS650 powering an S1.
For a month it powered an overclocked S1 (~400W) through 1 cable with 2 PCI-E connectors. The PCI-E wires were running rather hot, barely tolerable to touch. After a month I added additional wires with a couple of 2-molex-to-PCI-E connectors, it dropped the wire temp, and the PSU has been working fine for about five months since.
So, VS650 should be fine for a single stock clock S3 (~350W). And adding a couple of 2-molex-to-PCI-E connectors would allow for overclocking and/or give you additional safety margin.