Here is a useful tool that you may want to take a look at: http://www.antec.outervision.com/ , Just keep in mind this number is to give you a good idea of the power your PC will need and it is in most cases a high estimate.
Yeah sure is. Then we have to look up all your PC parts and thier max power consumption, add those up and put a little headroom on there for you.
I know those calcs are not the best but its easy to refer people to them, I am still unsure about there CAP aging and high-end PC and how many watts they add. I usually go with Antec because its clean and easy and not as out of line as ones like Newegg's or Corsair's, Outervisions site is kind-of ugly