most of those power calculators take maximum load power for all components into account, and then probably add 20% more just to be safe. Unless you have a crossfire setup, and you're not using a pentium D, or FX chip, you're not going to be using more than 250W max. I was recently going to swap out my 485W enermax for a 380W seasonic, mostly because of noise, but also because psu's don't reach their highest efficiency if you don't supply a large load, and I'm sure my system is barely even pushing my psu. But instead, I'm just going to swap the fans in the enermax for something different. I know someone who was powering an athlong x2 4400, 5 hard drives and a x1900xt off a 350W antec SP. He had no problems,. He even overclocked and raised voltages. Everyone thinks they'll have "headroom" for future upgrades. Outside of video cards, the rest of the systems consumption is actually dropping every year, so these 1KW psu's are extremely overkill unless you're considering quad sli. Typical systems just don't draw that much power, especially when you consider much of the time you're idling.
