I wouldn’t argue if this were a build list with the PSU to be purchased. The question is whether the existing PSU will handle it safely, and while not ideal, the answer is yes for most GPUs.
Why ask him if you're going to respond with the answer immediately?
Doesn't that kind of defeat the purpose?
I'm not trying to beat this into the ground, but -- do keep in mind that the GPU manufacturer knows nothing about what the rest of the system looks like. So traditionally they've taken their GPU power draw, which they know, and added a gigantic fudge on top. (Maybe they are trying to cover for a dual Xeon setup, or something.) The GPU manufacturer recommendation is, unfortunately, completely useless.
The best way I've found to estimate power needs for GPU's is to look up a review that measures power requirements. Tom's hardware reviews typically do this, for instance. The PCpartpicker estimate tends to run a bit high compared to actual draw from actual reviews, but it's not crazy high.
Incorrect. A PSU rating is its output rating. The efficiency is the input to output conversion efficiency. A 500w PSU running at 100% of rated load and (say) 90% efficiency draws 550w from the wall and delivers 500w to the load.
It makes all kind of sense if you figure that the rating a buyer needs is the output rating. An input rating would be a lot harder to deal with since you'd have to apply the efficiency curve as well.
It makes perfect sense. Maybe you're not the one to make sense? ;)