you shouldn't worry about idle temps, because load temps are hotter right? i'm not sure about the new AMD cores, but generally once your CPU gets to 50C+ its time to get better cooling.
...? what do you mean max. the max in the bios is 200, which is the 1 to 1 ratio with the FSB, you can either select 200, 166, 100, or some others ones on the DFI board. and that will determinte if it will run 1:1 5:6 etc etc
And how is the choices simply that black and white? If he's only using 1.5vcore then I'd put around 1.6+ in there and raise it up until it 200 like you basically said.
However not all boards have just 133, 166, and 200 as the options....so thats a limiter as well