When I was looking at lighting a 36” I priced out reef bright 250w MH fixture with their ballast and radium bulbs with hanging kit from brs was around $500. 32” reefbreeders led is $590 and have tank mount options and pulls 230w full blast. Not really dissimilar and I personally prefer the RB to MH alone. RB are used by battlecorals aquaculture and some amazing tanks as well.
Not sure I would be happy with an approx 8 inch wide light source long term. 12 to 13 inches would be minimum for me on a 36 inch long tank that is probably 18 inches wide lets say.