I need a new PSU and most popualar PSU at newegg are the 650-TX & 750-TX but neither have the ''2.91'' in there description is this important ? Do I need this ? The TX-850 & 950 both have it, but not the 650/750 ? I just built a new PC with a I7 & GTX460.
CORSAIR CMPSU-650TX 650W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 Power Supply
CORSAIR CMPSU-750TX 750W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 Power Supply
CORSAIR CMPSU-850TX 850W ATX12V 2.2 / EPS12V 2.91 SLI Ready CrossFire Ready Active PFC Power Supply
CORSAIR TX Series CMPSU-950TX 950W ATX12V v2.3/EPS12V v2.91 SLI Ready 80 PLUS BRONZE Certified Active PFC Power Supply
EPS is more of a server and super high end power supply standard, as long as they are at least ATX12V V2.x/EPS12V you wont be able to tell the difference between them, its just very minor revisions usually and often times, like on the 650TX and 750TX the exact version of the revision isnt marked down simply because revisions are small enough that even through 10 revisions its likely still fully compliant with the latest one.