I agree that you want to put as much flow as reasonably possible into the tank, but with most of it created through powerheads or closed loops. You don't need to put any more flow through your sump than your skimmer, heater, chiller, etc. can handle; otherwise, you would be cheating that equipment's effectiveness.
For example, I only run 1,100gph through the sump on my 300g reef (the skimmer only processes 800gph or so, but the heater and chiller seem to work well with this amount of flow). If I crank it up any more, I start to have microbubble problems, and the skimmer doesn't seem to pull as much gunk out of the water. The rest of my water movement comes courtesy of a Tunze Wavebox and a closed loop run with a pressure-rated pump and eductors.
I would highly suggest looking at eductors to enhance your water movement. They are great for large tanks and only run about $25 a piece. Paired with an appropriate pump, an eductor can increase in-tank flow by 4-5x's!
I also agree with the 400W suggestion for lighting. 3x400W over my tank (92"L x 30"W x 24"H) light it up very well. I use PFO M59 magnetic ballasts, but plan to switch to Coralvue electronic ballasts once finances permit. The Coralvue ballasts only use slightly more than 3A a piece, as opposed to the 4.5-5A that M59 ballasts use, or the close to 4A that 250W HQI magnetic ballasts use, and still allow the 400W bulbs to put out great PAR values.
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