there will not be enough of a difference to notice.
the only time an electric fan really has any benifits with a factory motor, is when you spend a lot of time in very deed mud and get tired of destroying your fan clutches. just make sure there is a switch for it so you dont break the fan blades.
also, what makes you feel you have lost power? was it a jump to taller tires? if so, the only wa yto gain back that lost power is to install deeper gears. if your still rolling stock, or are geared up for the current tires, then you may just need a good tune up.