Awesome Jim!! I can't wait to see the results. Let me enter my hypothesis:

65K - will show great growth, but poor coloration.

Actually, After running Iwasakis for a year, I noticed that vividly colored Acropora respond the worst as far as coloration goes, but growth is excellent. My Montipora Digitata (purple and orange) did not fade nearly as much as my Acros. The Acros browned out. If you could, you should throw some colored acro frags under the different lights. I think it could be a valuable addition to your experiment.

10K - moderate growth and coloration.

20K Radium - Marginal growth and good coloration

20K XM - Good growth and coloration

I have been running 2 250 watt XM bulbs for about a week and a half and have already seen noticable changes. Light penetration is excellent on my 26" deep tank. Color is excellent and needs no daylight or actinic supplimentation. Corals have responded already. I had a tricolor acro that had browned out and the purple is already returning. Also, another light brown acro frag is now turning blue. I just hope the XM's have a better life than the Radiums. Can't wait to see how they stack up in your experiment!