Graphics cards that should work with that power supply ranked in order from best performance to worst performance:
1. GeForce GTX 650 - requires one 6-pin PCI Express supplementary power connector even though measured power consumption shows that the card's maximum power consumption is less than 69 Watts while running FurMark or GPGPU stress testing
2. GeForce GT 640 or Radeon HD 7750
3. Radeon HD 6670
For a system using a single GeForce GTX 650 graphics card NVIDIA specifies a minimum of a 400 Watt or greater system 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.
For a system using a single GeForce GTX 640 graphics card NVIDIA specifies a minimum of a 350 Watt or greater system power supply that has a maximum combined +12 Volt continuous current rating of 20 Amps or greater.
For a system using a single Radeon HD 7750 graphics card AMD specifies a minimum of a 400 Watt or greater system power supply. The power supply should also have a maximum combined +12 Volt continuous current rating of 20 Amps or greater.
For a system using a single Radeon HD 6670 graphics card AMD specifies a minimum of a 400 Watt or greater system power supply. The power supply should also have a maximum combined +12 Volt continuous current rating of 20 Amps or greater.
The system power estimates are based on an Intel i7-920 system. If your system configuration uses less power than the Intel i7-920 system then you should have sufficient PSU +12V rail capacity.