I have 1 300w heater (cant remember the brand off the top of my head).
Just bought the TC-10 as well and will have the same setup as Morri (once I get round to wiring it up).
Having lost a lot of livestock from a malfunctioning heater I would say that a heater controller such as the TC-10 is a must have bit of kit. Not only will it stop your heater from cooking your tank if it all goes wrong you can also use it to cool the tank as well (be adding a fan or chiller to it).
The TC-10 seems to be the best option out there for temperature control gear. At around £30 a well it should be on the top of everyone's equipment list when setting up a tank.