The graphics power cord supplied with the EVGA 550Ti card is two 3 molex males pig-tailed down to the 6 pin that connects into the back of the card..
So my questions is.. Once I plug the 6 pin end into the back of my EVGA card do I have to supply power to both 3 pin molex ends or just one? I also have two connector sockets on graphics board
Well if your PSU has a pci-e power connector then connect it to your video card. If not then those molex adapters are to be used as a pci-e power connector. Yes, you do have to plug both in so the resistance is less thus offering more stability.