For idle testing, the computer was left running with no applications aside from GPUz open for 10 minutes. For load testing, I fired up Furmark v1.7.0, still with no AA and a resolution of 1440 x 900, which maxed out each card more than any other benchmark/application can.
For Temperature testing, all fans were kept at auto in a closed case with no side fan and ambient temperatures of ~75F. The following maximum sustained temperatures were recorded:
Sitting at idle, the HD 4670 just beats out the AXLE GT 240, which itself gets the lowest temps at load. The 9600 GSO is significantly warmer at idle due to the fact that it does NOT throttle its GPU/Mem/Shader speeds at idle usage like the other two cards do, and boy do they.
Again the HD 4670 is just a little bit more efficient at idle than the AXLE GT 240, but uses 13% more power at load than the GT 240. Again, the 9600 GSO is hurt by not throttling its clock speeds at idle, but at load it is actually close to the HD 4670, which does not require a 6-pin PCIe power connector.
And now for the fun part: the Overclocking.