Hexus takes a look at a bunch of 400 to 500W power supplies:
We soon all learned that one PSU's 500W is another PSU's 300W and so quality became an issue. Just once we'd got in our heads who makes good PSUs and who makes bad ones, the power wars kicked off again, and now we're seeing PSUs in the range of 1kW. Where will it end?
Of course, with graphics card and other component manufacturers cramming ever more current-sucking components onto their cards, it might not end any time soon, despite efforts to reduce device power consumption. A super-high-end system really does need a super-high-end PSU to power it. Luckily for most, however, something a little more modest will probably suffice.