+1The Hammerhead is 1 1/2 on both sides.
I'm assuming this is a joke. There are certainly enough proper tank builds of well over the 200 gallon mark that use power heads, unless you consider Tunze and Vortechs something else. The link earlier is a 1200 using 8 Vortechs. Large pumps cannot match the GPH a pair of normal Tunze's can do and at 1/10th the electric. From a DR standpoint I can power a single Tunze/Vortech for hours on a small battery, to do the same with a Hammerhead would require a room of batteries.
Just my opinion but the old ways of thinking large single pumps are wrong, I can protect my system from power/pump/heater failures a lot easier going modular. Why would we not build our systems without taking this into account?
In most of the large of builds I have done, I do use one large to pump to power the main returns and accesories ie. Ca Reactors, Media Reactors, etc. However, circulation within the tank is usually based on a system of Vortechs or similar utilizing a battery Backup should the power ever go down. Remember tank turn over is not just limited to water going down the overflows and through the sump.
I think you are on a good path. I would however recommend using 2 - 7" Filter Socks at one time. I also recommend a stock in them so that you can keep several clean so that they be changed out in an instant.
Good Luck! Looking forward to see how the build goes!