James, we are talking about two different issues, control and drive... as per control (this was your original question) I still recommend you implementing some sort of PID. For drive, you have to deal with two 9 Amp loads which is a lot so Mr. Charles approach is the right way to go. Some time ago I repaired a small peltier commercial fridge (used for an energy drink promotion) and it had a good EMI filter, a small control board and two solid state relays, very simple indeed...