Is my 700w PSU enough to run 2x 680 GTX in SLI?

Solution
For a system using two GeForce GTX 680 graphics cards in 2-way SLI mode NVIDIA specifies a minimum of a 750 Watt or greater system power supply that has a maximum combined +12 Volt continuous current rating of 53 Amps or greater and that has at least four 6-pin PCI Express supplementary power connectors or two 6-pin and two 8-pin PCI Express supplementary power connectors depending on brand and model of the graphics card.

Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Total Combined Continuous Power/Current Available on the +12V Rail(s) rated @ 45°C - 50°C ambient temperature, is the most important factor....
For a system using two GeForce GTX 680 graphics cards in 2-way SLI mode NVIDIA specifies a minimum of a 750 Watt or greater system power supply that has a maximum combined +12 Volt continuous current rating of 53 Amps or greater and that has at least four 6-pin PCI Express supplementary power connectors or two 6-pin and two 8-pin PCI Express supplementary power connectors depending on brand and model of the graphics card.

Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Total Combined Continuous Power/Current Available on the +12V Rail(s) rated @ 45°C - 50°C ambient temperature, is the most important factor.

Overclocking of the CPU and/or GPU(s) will require an additional increase to the maximum combined +12 Volt continuous current ratings, recommended above, to meet the increase in power required for the overclock. The additional amount required will depend on the magnitude of the overclock being attempted.

The Thermaltake Toughpower 700W (W0105RU), with its maximum combined +12 Volt continuous current rating of 56 Amps and with two 6-pin PCI Express supplementary power connectors, is electrically sufficient to power your system configuration with two GeForce GTX 680 graphics cards in 2-way SLI mode but it is deficient by two 8-pin PCI Express supplementary power connectors.

I would recommend that you upgrade to a power supply that actually has the appropriate number and type of PCI Express supplementary power connectors.
 
Solution