A GeForce GTX 460 has a maximum graphics card power of 160 Watts. This means that the graphics card itself may draw up to 13.3 Amps from the +12 Volt rails.
For a single GeForce GTX 460 graphics card system NVIDIA recommends a power supply with 450 Watts or greater with a +12 Volt continuous current rating of 24 Amps or greater and with at least two 6-pin PCI Express supplementary power connectors.
The Antec EarthWatts EA-500D Green should work just fine. It has a combined +12 Volt continuous current rating of 37 Amps and it also has one 6-Pin and one 6+2-Pin PCI-Express power connectors.