Originally Posted by hednik
So I still get quite confused by how to really read all the numbers I guess. A good overclock on a 125W CPU, a HDD, fans, cooler, other parts. Then put in two former high-end cards under stress of gaming and you sure come close to the limit with it all. What exactly is a good buffer to have ? It seems like this is not taken into account.
Noting to get confused about, you're working with benching numbers which even though important, are not relevant for this scenario.... as far as I understand the thread, he's not going for HWbot rankings with this setup, he's using it for games.. and 650W is plenty for that.
As far as benching goes, he would be smart to avoid running synthetics for the CPU and VGAs simultaneously for extended periods of time(for that would indeed stress the PSU too much).
In regards to buffer, ~10% for mainstream units(like the one mentioned here, none for high ends(Seasonic X, Rosewill Capstone, Kingwin Lazer Gold/Platinum and the likes) and at least 20% for poor units(those that can't do full power without massive regulation issue or poor output quality)