Efficacy from wattage is not really my concern at the moment, as I can sacrifice efficacy for less heat.All things being equal, I am looking for the coolest (heat wise) option, to get that 900 lumen output.From what I read and understood so far, using more leds at a lower output will be advantageous in many ways, but also for heat issues ? or is it that heat is the same for the same total lumen output regardless of leds used? I fail to see on the Cree spec sheet the temperature behind the emitter at different lumen output. If 2 emitters at 150 lm each dissipate both together even 10% LESS heat than 1 at 300lm, that would be ideal.The reason I must know is that I am experiencing thermal shutdown on the driver with 3 leds when they are on just after 20 minutes. I would imagine that using 6 at reduced power will produce less heat just enough so that I can avoid that situation.