I have an acan 600 and I dont agree with this at all. I have my fixture 13" above the water line. Running 55%w 100% blue at my brightest point of the cycle.I gave you a suggestion bud. You get what you pay for. The Reefbrites are VERY high quality. If your dead set on LED than ditch the Acan and go AI. At 10" above the water you'll have about 24 square inches of coverage from a single unit. Slightly more if you can go a little higher. I've seen both the Acan and AI in person and the output of the AIs is a step above the Acan IMO. May be your best route. Still think a single 24" RB may be all you need. Their output is crazy.
I could broil a pork chop under it at 100/100.
I saw the AI at 100/100 at PW in Carle Place last night nad "to MY eye" The AI doesn't seem as bright.