The Radeons switch to an ultra-low-power state when the display goes to sleep, which explains the first round of numbers. Under load, though, the GeForce GTX 650 Ti 2GB AMP! demonstrates excellent power efficiency, drawing only 10W more than the 7770 Black Edition.
Noise levels and GPU temperatures
The GTX 650 Ti AMP! is a smidgen louder than the rest of the pack at idle, but it's quiet under load—certainly quieter than the Radeon HD 7850 1GB.
Despite its low noise levels under load, the Zotac card's cooler works very well, keeping the GPU temperature at just 60°C. The power-hungrier Radeons run hotter, which is no surprise.