After seeing them in person I was sold. I put a pair of blues over a 36x36x24" cube. LOVE THEM!!!!!
2 is not enough if you want full coverage, but I wanted a spot light effect over black sand so it works great for me.
I am not in love with the stock AI rail system. You cannot tighten down the screws with thier configuration so the lights are loose on the rack. If you tap your own angle iron or used an aftermarket alternative as Paul has done you will be able to more adequately secure the lights mounted.
A word of caution, even if you had previously intense MH lighting... it will burn the CRAP out of your corals if you are not careful. I set mine up, then had to go away for a week. Mistake. I had my light cycle approx as follows (18" high over 24" of water)...
11am-12pm 20%B, 20%RB, 0%W. 45 min ramp up
12pm - 5pm 75%B, 40%RB, 100%W 45 min Ramp up
5pm - 8:30pm 50%B, 30%RB, 75%W 30 min ramp up
8:30-10pm 30%B, 30%RB, 10%W 30 min ramp up
10PM 2%B, 0%RB, 0%W with Lunar cycle on, 30min ramp up/down.
That 5 hours of intense light NUKED my tank. Lost everything but a few soft corals that could cover up and my RBTA who just moved down under a rock.
I have now dialed back the lighting for 3-4 weeks of almost half that and things are happy and responding. The Blue spectrum is dangerous I think if you don;t pay attention to it. Seems like you need a lot more light, but you don't.
While expensive, so far now that I know better after the loss, I am very happy with the lights and the control I can get over the times and %'s.