The amount of heat given off by any one particular light bulb is going to be the same no matter what reflector or not is used. The big difference is the way you deal with it. Air or water cooled reflectors help you get at it immediately; a fan will blow it away from the bulbs but you are still left with the heat, only it's dissipated. The bottom line is that the heat issue must be dealt with or else you will surly stagnate the plants growth or worse yet, kill it. 1.000 watt bulbs have a significantly higher heat to watt ratio over 600 watt. I use splitters that change y output from a 1,000 HPS ballast to two @ 600W MH and I absolutely love them. Two reflectors from one ballast, I increase the footprint almost 2X, less heat from the two vs. the one bulb, and save dollars on not buying two ballasts.