When using a quality 1000 watt PSU, if you run more than 1000 Watts should it cut all power and reboot, od do they just burn out? I ran a little more than 1000 watts on my ultra x3 1000 watt psu and I blew it...
A really good PSU can sustain some Watt in excess but not for a long period without incurr in problems. But you've to check the A in the various voltages: I've see a 650PSU that can sustain up to 730W.
Due to the technology used to build them normally good PSU shall cut out power if you use them over the specs, but is not unusual that they blew up if the over power is all on 1 line (I see your PSU can sustain a max of 840W on 12V, there are PSU of coolermaster rated for 800W the can arrive to 780W and the 1000W can sustain 984...)