In that scenario, can you safely use two 8-pin to 2x 6+2 pin cables to connect the GPU (note: this would leave one of the 6+2 pins unplugged). One rumor has it that the upcoming 3000-series cards from Nvidia might utilize 3x 8-pin connectors.
My research so far has informed me that an 8 pin provides about 150W of power. If that's the case, then how can one 8-pin connector effectively supply two 6+2 pin connectors? However, based on reading (such as PCI-e Power - Does 6 + 2 Equal 8?) an 8-pin is effectively the same as a 6+2 pin. A common cable included in modern modular PSU's is the 8-pin to 2x 6+2 pin.
