A reference clocked GeForce GTX 460 will draw a maximum of 13.3 Amps from the +12 Volt rail(s) under full GPU load.
I wouldn't recommend it with that power supply unit.
The PSU you have is manufactured by HEC/Compucase. It is a version of the 300W HEC unit re-marked by Thermaltake as having 430W wattage. Xbit labratories reported that at a load of about 380W, the PSU’s switching transistor overheated and burned down in the power supply.