I'll go back to my old system which was a 75 gallon tank.
My initial lighting was 1 400 Watt @ 14K plus 110W of P
C atinics. I never had any great growth with this set up, and eventuially made some changes.
My end set up was 1 400W @14,000K and 250W @16,500K plus 220 Watts of atinic lighting. The Atinics were on 12 hours per day, the 250W was on for 10 hours a day and the 400W was on for 8 hours per day.
The half of the tank with the 400W MH did have more color than the other side however actual coral growth was considerably faster on the 250W side. Visually looking at the tank the 250W side looked brighter even though it had less wattage than the 400W side. This I will atribute to the color temperature differences between the bulbs.
If I were doing this again as a 75 gallon tank I would go with SE 250W bulbs looking at the highest PAr 10K's I could find. Then I would suplement with T-5's in the 420 and 450 nm range.
My new tank is a 120 gallon that is in process. My lighting plans for this tank are twin 250W SE using XM 10,000K's plus 4 T-5 bulbs with a combination of 2 420nm, 1 450nm, plus a so called Blue Plus bulb.
The other thing to consider is goiing with straight T-5's on you 75 gallon tank. However, I would use at least 6 bulbs with a least a pair of 10K's for starters. Remember though that bulb combination can change the looks of your tanks drasticly, and what one person might consider too blue another person might consider not blue enough. There is a lot of personal taste involved with these bulb selections.
Dennis
Dennis