If it is significantly stronger, may want to ease them into it -- if no dmmer, than with height.. works well either way.
I'd find a light with ~70-85 diodes per square foot utilizing samsung lm301b diodes (white) and a few 660nm red diodes mixed in. By doing this you'll have the efficacy and coverage. Unless you start adding CO2, this will be nearly as strong as you'd want.
one other suggestion -- overshoot a bit on diodes per sq. foot. Allows you to offset slow dim over 50-60k hours of use and maintain same exact coverage and intensity as day 1.