I haven't decided what I'm going to do about a video card. According to the article here that lists best cards for the money, I should crossfire 2 4870's. Or maybe get an HD 5850. Still have to do more research for that one. If I Crossfire I will need a new PSU.
For that site that you linked, if I did everything right then my 600W should be alright. It lists 576W for my needs. But thats with system load at 90%. If I bump it up to 100% I would need 640W.