For a system using a single GeForce GTX 560 Ti graphics card NVIDIA specifies a minimum of a 500 Watt or greater power supply that has a combined +12 Volt continuous current rating of 30 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(s) you are trying to achieve.
There are two COUGAR 560 Watt models that I know of and you didn't specify which one you have:
The COUGAR SE-series 560W (SE 560), with its combined +12 Volt continuous current rating of 41.7 Amps and with three 6-pin and one (6+2)-pin PCI Express supplementary power connectors, is sufficient to power your system configuration with a single GeForce GTX 560 Ti.
The COUGAR A-series 560W (A560 CGR B3-560), with its combined +12 Volt continuous current rating of 40 Amps and with two (6+2)-pin PCI Express supplementary power connectors, is sufficient to power your system configuration with a single GeForce GTX 560 Ti.
What is your graphics card budget if you want more suggestions?