Don't worry about the low fan speed (at idle, anyway). The Evo fan runs very slow at boot and idle, assuming that the temps are low, so there's no problem at all with that.
Try stress testing the CPU to see what happens and use HWMonitor to check the fan speed. If the speed doesn't go up with the temp rise, then you may have an issue.
My guess is that your CPU is running cool enough at boot and idle that the fan doesn't need to spin any faster, but when you put some real stress on it, the speed will go up.