1700 watts per light isn't much (it's watts, not watt-seconds like a strobe), and you only have a choice of 2-lights or 4-lights on with each unit. I also question that each lamp is equal to a 425-watt tungsten lamp to begin with. (425 X 4 X 2 units = the claimed 3400 watts.)
The way it's shown using an umbrella wouldn't work well either: with no reflectors, most of the light from the lamps is going sideways, not into the umbrella.
