I have the 8600GT and i was looking through the guide, and it does not tell me what the temperature readings should be when idle. It did come with a temperature reading program for the GPU.
oops, my bad...
On the other hand i just got my Computer up and running this morning, so it hasent really had time to overheat i guess. Im guessing over time the normal temp will go up.
Well if your 8600GT came fresh out of the box just today, then the thermal paste has to set in. When I got my VGA, fresh out of the box, it was running about 55C+ idle, but it's gone down.
I'm usually about 56C idle. But 46C is good for any graphics card. I don't think the 8400-8600 series' get all that hot, either. That's why many of them are only heatsink cooled or have a tiny fan.