i have a friend up the block from me who has a 120g saltwater RR tank. he has 3 250 watts MH's the blue white tint. looks really nice. be prepared might need a chiller.
I run two 250 watt single ended XM 10,000K bulbs powered with Ice Cap electronic ballasts and two 110 watt 46.5" URI super actinic VHO bulbs also powered with an Ice Cap 660 ballast on my 4' 120g reef tank. Very satisfied with the color and intensity.