I'd avoid drilling any extra holes, but you might want to make sure your closed loop drain hole has enough capacity to cover any amount of circulation you want; at a minimum, a 1.5" bulkhead. You could probably drain to two pumps if needed with that, or at least one biggie. Any returns can go over the tank top.

Are you going with the oceans motion? I'm in agreement with avoiding the tunze set up. To me, it's just WAY too much money for big ugly powerheads in the tank. They do save energy, though, and simplify the water movement task. But, I bet the oceans motion with a monstro closed loop pump (ampmaster/sequence) will really give your tank great flow.