Neither of the replies above is terribly helpful or accurate.
Manufacturers inflate their recommended requirements to cover themselves against the huge variations amongst power supplies. The card itself has a tdp of 170W so in most systems you are likely to draw more than 350W for your entire system.
This would imply that any 400W+ PSU would do the job, however the rated wattage will be spread across multiple voltages. 12V is the only real concern, and any good quality PSU is likely to deliver 90%+ of its wattage at 12V, though a poor quality/antiquated PSU might only provide 50%.
Whether or not your 460W PSU is sufficient depends both on your other components, and what model of PSU it is. Additionally, most sub-500W PSUs tend to come with a single 6 pin PCIe power cable, the GTX760 requires two of these. It is possible to use molex adaptors to make up the shortfall, but it's a poor solution.