For a system using a single GeForce GTX 680 graphics card NVIDIA specifies a minimum of a 550 Watt or greater power supply that has a combined +12 Volt continuous current rating of 38 Amps or greater and that has at least two 6-pin PCI Express supplementary power connectors.
Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Total Continuous Amperage Available on the +12V Rail(s) is the most important factor.
Overclocking of the CPU and/or GPU(s) will require an additional increase to the 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 you are trying to achieve.
The Corsair Gaming Series GS600 (CMPSU-600G), with its +12 Volt continuous current rating of 48 Amps and with two (6+2)-pin PCI Express supplementary power connectors, is sufficient to power your system configuration with a single GeForce GTX 680.