I don't know if it's the same as the 6 and 7 series GeForce, but if it is, the max is at 120*C. I wonder if Willz will answer...I'm pretty sure he has one.
60 degrees idle is perfectly ok. When I had an 8800GTS I had it overclocked to 620/980 and it idled at about 64, expect it to get into the 80's at load, its fine :)