Temperatures & Power Consumption
For both temperature and power consumption load testing, Furmark v1.8.2 was used for 5 minutes when both leveled off. Idle results are from 15 minutes with no applications running. For the crossfireX temperature results, the average temperature between cards was used (GPU0+GPU1 /2).
Temperature results are basically all over the place, with the Batmobile cooler on the XFX Radeon HD 5770 beating out the Arctic Cooling design on the HIS Radeon HD 5750, but you certainly cannot discount how loud and obnoxious the Batmobile cooler is when turned up above default. The mix crossfire setup actually put both cards at 77C load, where idle temps still varied between the two. The BIOSTAR GeForce GTS 250 used features a 3-heatpipe copper heatsink which does very well at cooling especially at idle, but only a single BIOSTAR GTS 250 is currently available on Amazon
Idle power consumption is really a game of idle power states, as shown back in the GPUz shots. Both ATI cards have an idle power state at 157MHz core and 300MHz memory, whereas the NVIDIA cards have their power states at a much higher core clock of 300MHz, but a lower memory clock of 100MHz.
Both ATI cards also had great load power consumption, well under the GeForce GTS 250, and even the mix crossfire setup used less power than the single GeForce GTX 260, which was very surprising.