All the cable connections are the same. From what I'm reading, it's a matter of having different 12V rails "over current protection. If you left many peripherals consume the power on only one 12V rail, it may trigger the over current protection and shut down the system." So I guess it's to make sure that you have enough power for whatever you need to plug in. Not sure what the GPU needs, V3, 4, 5 or V6, but perhaps it doesn't matter?