Thanks shake. I knew there was quite a difference in the lumens between the two. The 2 bulbs I bought are rated at 20,000 for the MH and 30,500 for the HPS.

My concern is the amount of heat actually generated by each. Since, as you already know, I'm running this inside a small grow tent I'm just wondering if I should be thinking about adding a second circulating fan aimed at the reflector, add an insulating blanket like the one hydroinnovations makes or even add a "Y" splitter to the exhaust ducting to pull out hot air from above the reflector. Or......... all of the above.

Just trying to plan ahead rather than frantically trying to deal with any additional heat when I switch the bulbs.