i need to know why they dont sell 600watt mh bulbs. Im going to be buying about 12 600watt fixtures but need to kno why they dont have mh bulbs?!!! Is the conversion bulb not as effective? Am i better off getting lower wattage lighting systems or should i just get 1000 watters. Id rather get 600 since they are most efficient. I need to know more about conversion bulbs if thats what i have to resort to. thankyou