My tank is a 65g and those are two Koralia 3s in there. I am only two months into the hobby myself, but my undertanding is that you want to create zones of flow so that you can support both high and low flow corals. At the same time, you don't want any dead zones. To accomplish this in my tank I have the two power heads pointed at each other and down a bit so the flow meets in the center of the tank. That gives me a very turbulant high flow area in teh middle water column, and leaves my upper and lower water column with reduced flow but not stagnate.
If I were you I would just experiment. try different configurations and then sprinkle sand into the water and watch how it moves through the water column.