If you want to change it, modify the min fan speed and desired fan speed, they function as they describe. Reduce the minimum and set the desired fan speed to a minimal setting, it will automatically increase fan speed as cpu load and heat increase.
Than your particular motherboard isn't compatible with speedfan and therefore, probably incompatible with any other fan speed controllers. If it is really bugging you, you can get yourself a hardware fan controller, or you can get a new heatsink for your cpu. I am guessing that you have a oem heatsink right? 80mm fan and it's pretty noisy.
After looking at your mobo specs I found this comment "but my system fans keep running at full speed. Have to use SpeedFan to keep the processor fan at 2000 rpms. Replaced one fan with a quiet molex-powered fan because SF wouldn't work with it. However, Scythe makes good fan control modules, so I'm going to invest in one soon."
possibly, but if you get a heatsink that is larger than 80mm's then it won't be as loud. The greatest way to know how loud a heatsink's fan will be is to look at the max dB it can output. anything past 30 dB or dBi can be considered noisy. Stock heatsinks run at about 38 dB.