Over the last several months, ATI has been put out the better of the video cards, such as the 5800 series. I my self though , am a fan of Nvidia fan. The 460 is a beast, your power supply will need alot of amperage on the +12dcvolts rail, probably 30 amps if you are running one card, 60amps if running SLI.
Recommended Power Supply
Here is Guru3D's power supply recommendation:
GeForce GTX 460
On your average system the card requires you to have a 450 to 500 Watt power supply unit.
GeForce GTX 460 in SLI
A second card requires you to add another ~200 Watts. You need a 650 ~700 Watt power supply unit.
There are many good PSUs out there, please do have a look at our many PSU reviews as we have loads of recommended PSUs for you to check out in there. What would happen if your PSU can't cope with the load?:
bad 3D performance
crashing games
spontaneous reset or imminent shutdown of the PC
freezing during gameplay
PSU overload can cause it to break down
The GTX460 has better specs then the 5770, but uses more power.
Here is a link to current and upcoming DirectX11 games.
http://en.wikipedia.org/wiki/List_of_games_with_DirectX_11_support