A good 500 watt PS is fine.
I have a coolerMaster Xtreme power 500 and I run:
4870 1GB DDR5
3 HDDs and 1 DVD Burner
Off of this:http://www.newegg.com/Product/Product.aspx?Item=N82E16817171018
Note that the reviews are right this particular supply is LOUD. I don't mind because this is my gaming rig and I usually turn it off at night, but if you don't plan on doing that, you may wanna shell out a bit more for a quieter supply.