With CPU + SLI on load I see the figure around 850-860watts on the kilometer unit which is plugged in the socket.
On furmark I managed to see a figure 1050W on the kilometer once. I never tried to run it again that time.
But now on SLI I cannot even get furmark to get running. Just shuts down computer.
I don't think nothing is wrong with the kilometer. I just don't know where there is massive jump from 1GPU to SLI of around 400W or more when it furmark.
Ah, the the wattage reading was from the wall socket (I thot it was converted DCwatts). So, makes more sense.
Still don't have an idea why a 300w max card(2nd gpu) can pull more than that, but I would agree with what you already decided to do and replace the PSU.