It is the graphics card that mostly determines the psu you need.
For a GTX460, you need a 450w psu with 24a on the 12v rails, and two 6 pin pci-e power connectors.
Do not go cheap on the psu. My short list of quality psu's would include Antec XFX, PC P&C, Corsair, and Seasonic.
Any of their 450w units or better will do the job.
Today, XFX seems to have the best pricing.
Here is their 450w unit:http://www.newegg.com/Product/Product.aspx?Item=N82E16817207012
The 650w unit will power any single card out there.http://www.newegg.com/Product/Product.aspx?Item=N82E16817207007