I use a rapidled par38 over a 20 gal that I have its a 20 high that I modified onto its side. Its 24" long 17" wide and 12" tall.
I use just one of the par38 bulbs over it and its growing my zoas and I keep ricordea in it. That is as far I think I could go with it with coral
Mine is about 8 inches above the surface of the water so I couldnt tell you about if It was put up higher.. My slanted walls restrict that..
Other than that I love par38 bulbs because I have a planted tank that I use a track light from a hardware store for with LED bulbs. I just added another 2 feet and another track lamp that I sawed the covering of so I can fit the bulb onto it.
But really I think it boils down to what your looking for.