For a system using a single GeForce GTX 650 Ti graphics card NVIDIA specifies a minimum of a 400 Watt or greater power supply that has a maximum combined +12 Volt continuous current rating of 20 Amps or greater and that has at least one 6-pin PCI Express supplementary power connector.
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 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 OCZ ModXStream Pro Series 500W (OCZ500MXSP), with its maximum combined +12 Volt continuous current rating of 36 Amps and with one 6-pin and one (6+2)-pin PCI Express supplementary power connectors, is more than sufficient to power your system configuration with a single GeForce GTX 650 Ti graphics card.