Why not use Speedfan? I'm using it on an nForce 4 board (Asus A8N5X) and it controls the CPU fan perfectly.
I'm running a 3800X2 overclocked to 2.4. With a Ninja and Cool n' Quiet, the fan is off most of the time. Only comes on when I play a demanding game or run Prime95. Even then, it's limited to 60% of its top speed, and usually only goes to about 40%, so it never gets very noisy.