I used flexwatt for years with nothing more than a homemade dimmer switch controller. It worked fine. I'm probably going to get roasted on this one, but the person with a small collection does not need to buy the expensive thermostat controller. I had my racks set up with one extra tub, set up just like the rest. I ran a a cheap thermometer into this tub to get an ambient temp. I set the flexwatt temps with the use of a homemade dimmer and everything was fine for years.
Sorry if I fly in the face of conventional wisedom, but you don't need the fancy, high dollar gadgets.
Jim Smith