If you are really idling at 73c you need to do something other than adjust your fan speed. Do you mean under load it reaches 73c ?
Use one of the following and be sure to click on manual settings to adjust the fan speed. Resist the urge to increase clock settings.
EVGA Precision or MSI Afterburner http://www.evga.com/PRecision/http://event.msi.com/vga/afterburner/