Keeping the viscous fan might be the best option, an electric fan will never have the power of an engine driven fan (the viscous fan can take several horses from your engine, if it kicks in and works correctly it is able to move a lot of air).
The only advantage of an electric fan is that you're able to switch them off before a water crossing, so they won't hit the water and push water all over the engine bay.
The reason for the loud noise is the viscous unit. Basically the oil in the fan clutch is not spread out evenly after the vehicle has sat for awhile. When you start the engine, the unit is locked up and you hear the roar of the fan. After about 30 seconds of driving, the fluid is spread out inside the clutch and it resumes normal operation. Mine does the same thing .
I thought electric fans were a good idea but it probably cost me an engine. I slipped the liners in mine. It got very warm a couple of times when the electric fans could not keep up and I think this is what caused it. Also the temperature gauge doesn't do what you'd expect. It does nothing until it is too late then it jumps to the very end. It is so heavily dampened it might as well not be there. Might as well be an over HEATED light because it give no warning. For example when towing on a 5km incline it says dead centre until near the end of the hill when it shoots to the red in seconds. I know the engine temperature hasn't changed that fast.
New engine, proper fan and no problems any more. Expensive lesson.