How many watts?

Solution
For a system using a single GeForce GTX 660 (non-Ti) graphics card NVIDIA specifies a minimum of a 450 Watt or greater system power supply that has a maximum combined +12 Volt continuous current rating of 24 Amps or greater and that has at least one 6-pin PCI Express supplementary power connector. An exception is the MSI GeForce GTX 660 HAWK 2 GB that requires two 6-pin PCI Express supplementary power connectors.

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 at 45°C - 50°C ambient temperature, is the critical factor.

Overclocking of the CPU and/or GPU(s) may...
For a system using a single GeForce GTX 660 (non-Ti) graphics card NVIDIA specifies a minimum of a 450 Watt or greater system power supply that has a maximum combined +12 Volt continuous current rating of 24 Amps or greater and that has at least one 6-pin PCI Express supplementary power connector. An exception is the MSI GeForce GTX 660 HAWK 2 GB that requires two 6-pin PCI Express supplementary power connectors.

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 at 45°C - 50°C ambient temperature, is the critical factor.

Overclocking of the CPU and/or GPU(s) may 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.
 
Solution


Hi - yes a quality 450w unit will have the necessary +12v amps to
run a system with a reference gtx660.

You have a non-reference model using 2 pcie connectors as opposed to
1 connector in the reference model.

This implies it will draw more current, and I believe it would be prudent to
get something a little beefier (500-520w with2 pcie connectors) in your situation.

What is your budget & where are you located?