Power Consumption
With electricity becoming increasingly expensive across most parts of the world the need for computer components to become power efficient has never been more relevant. Graphics cards are often the most power hungry components inside a system so having an efficient graphics card is very important to keeping power bills under control. Power is often correlated to heat and so lower power consumption means a graphics card is likely to run slightly cooler and put out less heat into your system meaning your other components will run cooler with improved longevity. AMD and Nvidia have also both made power consumption an integral part of the way graphics cards dynamically overclock so the need for graphics card vendors to use efficient VRM and PCB designs is becoming important to maximise performance.
Find details of our power consumption methodology on page 3.
at £125, it takes it into 7850 1gb territory, I concur with your conclusion, its certainly overpriced, and limited by that 128 bit bus width, for the same money you could get the 256 bit 7850 1gb, the memory throughput is so much better, and will allow the VRAM to be overclocked, SCAN has an MSI 7850 1gb for just £123.34, making this 2gb 7790 variant redundant.
http://www.scan.co.uk/products/1gb-msi-radeon-hd-7850-4800mhz-gddr5-28nm-gpu-860mhz-1024-cores-hdmi-2x-mdp-dl-dvi-i