I can only speak for the Ranco. It comes with a 6 or 7 outlet power strip attached. Basically, you hook it up to one UTH and plug them all in, and it runs them all, based on the temp it gets from the one. The main thing would be to make sure that the combined wattage of your UTH's doesn't exceed the handling capability of your Thermostat. I believe the Ranco's are rated at 1200-1500 Watts and the average UTH, depending on size, runs between 8-25 watts. Hope this helps...
Rob