Ok, I am looking to build a desktop computer again, but I have been out of the game for a while. I am seeing a ton of 400-500W power supplies, but when I left that was nowhere near enough juice. So, the system that I would be building would be an AMD Athlon II X4 640, or a Phenom II X4 955BE, one DVD RW, one HDD, and a single HD6870. How much power am I going to need? Forgive the noobishness, when I left, I had had a Core 2 duo E4300 and a 3870X2 and a 750W power supply.