We are now able to find out what kind of power is being used by our test system and the associated graphics cards installed. Keep in mind; it tests the complete system (minus LCD monitor, which is plugged directly into an AC wall socket).
The ASRock X58 Extreme6 is a very power friendly board. While we expected the system to have a much higher power demand (simply due to the number of extra controllers on the board), we certainly did not see that in practice.
As a new measure, we are now monitoring the heat generation from the key components on the motherboard; this being the Northbridge, Southbridge (if it contains one) as well as the Mosfets around the CPU. The results are recorded at idle and load during the power consumption tests.
Heat is another item altogether. The much smaller heatsink on the X58 Extreme6 allows the temperatures to build up fairly quickly. It is not a big issue, but is one that needs to be kept in mind while you are planning out your case choices. Make sure you have good air flow over the heatsink for the X58 Northbridge.