Ok, still looking for answer if Corsair VS650 would be good to power 1 S3? I am not good with that stuff, so I will not be modifying server PSUs.
According to the table
http://www.corsair.com/~/media/Corsair/download-files/manuals/DC_Cable_consolidation_Rev_28.pdf the VS650 has only one PCIe cable, and therefore is not suitable to run an S3. You need two PCIe cables, four if you plan to overclock (plus higher wattage).
EDIT:- above assumes you don't want to use 4-pin molex to PCIe converters.
Hmm I dont know then any other PSU good for powering 1 miner, can someone help me?