The SPS that are from 8-14" in front of my MP20 are growing better than without it. granted there was a lack of flow before, hense the addition of the powerhead. I also have a stag that grows within a quarter of an inch of the housing itself. Just not directly in front of it. Take a look at page 11 of my build thread for a closer look at the vortech placement in realtion to the hawkins etc. Pics were just updated.
FWIW, the OM 4-way (AFIAK all OM motors rotate at this speed) rotates one RPM. Each nozzle gets 15 seconds wide open. With loc line nozzles that are fully adjustable, you can avoid blasting directly at any one coral. Or better yet, built with a manifold so there are eight or so nozzles, you can really get some flow down into the nooks and crannies of the rock work.
Dont get me wrong, Im not a total CL advocate, I have both in my tank. Six powerheads totalling over 7000GPH and a CL pushing another 5500GPH. Mostly the way you go depends on the look your trying to achieve. I dont like alot of clutter from six big old powerheads in order to get near 15000GPH
LOL Nowadays, I have six small ones.