I would like to get 3 200w
Cobalt Aquatics Neo-Therm Submersible Heater. You defintately want more then one heater where neither of them if the lock ON will over heat the tank. As an example, I beleive you would need 600w of heaters for your tank. Getting 2 x 300w would be great as if one breaks in the ON position, it alone will not over heat your tank as the other will never come on, if they both lock ON, it will not over heat your tank either (but may be pretty close, which is why I say 3x200w, chances of 3 locking ON together is less). If one locks OFF then the other will be able to keep your tank decent and alive until you get a replacement for the broken...make sence?
As for a controller, I would advise against a heater controller, I would go for an Apex Lite or Reefkeeper, the cost is not that much more then a controller (probably cheaper then a controller with Reefkeeper) and you get all the benifits and control of having an Apex.