I finally got my hands on a DVI to HDMI adapter and tested my system with a minimal configuration.
I removed my nVidia Geforce GTX 780 and all but 1 of my 8GB Corsair memory sticks. I then removed the rest of the components (motherboard, CPU, HDD) from the chassis and tested my system with integrated video enabled. Memory was set at SPD speeds (1333 MHz).
The Power Supervisor LED remains lit when the PSU is on but the system itself is off. On start-up I still get prompted with "Intel Power Supervisor has detected a catastrophic power event has occurred." Pressing a key allows the machine to POST and successfully boot to Windows 7.
In separate tests I moved the one remaining memory stick to a different DIMM slot and used a different memory stick. In both cases the Power Supervisor error persists.
It seems to me like a fault on the motherboard.
What is the next step?