Keith, really nice work on the tank. You are going to laugh when you turn the mh lamps on for the first time. I know it looks like there is a lot of light now.. Just wait!
It sure looks like you have done your homework. I think that as mentioned previously, placing the ballasts outside the canopy (if it's an option) may make them last a little longer and help cut down the temperature in the canopy too.
Did you go with magnetic ballasts, or electronic ballasts?
You don't really think you are going to be able to wait on the corals, do you?