Pump placement in 150 gal corner hex build?

I'm putting together a 150 gal corner hex as my first reef tank and was hoping to get some feed back on my thoughts for initial pump placement. I have an acrylic tank and need to drill some holes in the top for power cords, and don't want it to look like a honeycomb before I'm done. Hoping others out there have some experience with this geometry and can point me in the right direction.

I have a tank sketch attached. My plan is to follow the advice for the usual newbie. I'll start with soft corals and make sure I can keep them alive. Eventually, I'd like to have some stonies as well.

I have the following for circulation, which should give me about 20x tank volume...

Hydor Koralia 550 (2) - middle of water column slight upward slant
Hydor Koralia 750 (2) - top of water column slight downward slant
Mag 7 Sump pump - returns are top of water column slight downward slant

My thoughts are to use the 550's to keep some good circulation over the DSB along the back walls. This will also be a "quiet" zone for fish. I'll use the 750's and the sump returns to get flow out in the main tank. Do I need that much flow over the DSB or can the 550's be put to better use? I'll have sugar sand for the DSB with about 1/8" - 1/4" of 1-1.5mm gravel on top to weight it down.

It's not shown on the sketch, but the water column is 22" from the tank bottom during normal operation.

Any thoughts would be greatly appreciated!