You really need to measure this at the plug.
There is loss at each stage in a system, not just gpu and cpu.
The psu is a major factor in power in and power loss.
They can be found on our website here...
http://www.overclockers.co.uk/showproduct.php?prodid=NW-003-EN
They can be found on our website here...
http://www.overclockers.co.uk/showproduct.php?prodid=NW-003-EN