I'd say a proportional one, like a Herpstat, Helix, ecozone. It will serve you for ages and do what you want how you want and simply takes less messing with. The base model of Herpstat is about 105$ and is easy to use and works well. The Helix is a bit more check how much power you are going to control and the specs of the unit but I am sure both will be fine.