use msi afterburn. i've been able to lower the 290x to 125 watts average as per gpu-z. In my case i'm more worried on the fan noise so this voltage lowering brought the temp to the mid 60s and the fan to 60%, this while maintaining the sols at 337 to 347
What you see on gpuz is not the total power consumption of the card. 125w for the gpu only is possible but with the rest of power components on the pcb the real consumption is much more(about 200w). Check with wattmeter if you don't believe.
Agreed, but the numbers for the GPU are still absolute so any savings you see on GPU level are still 'real' power savings.