I ran one of the cards off of an antec 550W with 2x12 V rails w/ 19 A per rail. Thus, I really don't know if this tells me anything new b/c I'd run into the same problem if both connectors pulled off the same rail (for the record, both with this psu and the rosewill, I tried all combinations of pci-e and 4 pin molex + pci-e adapters). The kill-a-watt showed about 150 W before mining starts, and then 370 W with one card or 585 W with both cards. It would appear that 20 A probably isn't enough. Needless to say, the end result was the same as before. I will see if I can get my hands on a psu with larger 12 V rails.