Here are your rails/voltages:
+3.3V@30A; +5V@28A; +12v1@14A; +12V2@15A; -12V@0.8A; +5VSB@2A
You should upgrade your PSU anyways because it is unreliable. The brand is not good and using a wattage that will barely make it is risky. Is it possible to use a GTX 660 on it? Yes. If you have the spare cash I would invest it in a better PSU (preferably Corsair or Seasonic, although there are other good brands out there too).