I have around 9 Corsairs AX1200i . That is the best PSU I have seen and used by far. Although recently I started to use IBM BladeCenter DPS-2000BB server PSU. I am modding them myself with 4 6 pin pci-e connectors and using each of those to power one sp20. They are a single raid 91+ gold psus and are relatively cheap compared to the ATX ones.