I think you will really like the array design im thinking. cover the entire surface of one of these heatsinks
Bonded Fin/ Standard Parts with the luxeon rebels (only 3mm*4.5mm[13.5mm^2], 0.12"*0.18") and the LedEngin 10W and 15W LEDs(both 7mm* 7mm, 49mm^2). I was thinking of using one of those heatsinks with a width*length*height of 305 mm*371mm*152mm (12"*14.59"*6") , thats 113,155mm^2 cooling area with dual 100cfm fans. on that 113,155m^2 we could fit 8000 luxeon rebel LEDs or 2000 10W LedEngin LEDs!!!!
( with proper ventilation and cooling). the °C/W rating is .028°C/W, so for it to get 28°C hotter than it would have to receive 1000W of heat energy from the LEDs, voltage regulators, whatever needs to be cooled.
and maybe once i get some funds we could use water cooling systems (like this radio shack one but on a larger scale[will be much cheaper to make])
RadioShack.com - Computers: Components & parts: Cooling systems: Bigwater 735 Liquid Cooling System