FYI
Here's a chart of Mag pumps and head pressures: Charts for Mag drive application
Courtesy ReefCentral.com, here is a head loss calculator
This picture displays the return plumbing, including an additional horizontal valve feeding water to a refugium. The vertical section has a valve to bleed off excess water back into the sump. Details
To avoid too much flow to your tank, in case your pump is too powerful, you can put a "tee" in your return plumbing, and an elbow pointing straight back down into your sump. Then you put a ball valve on that. If the valve is wide open, the majority of your water will go straight back into your sump. The more you close the valve, the more water goes up to the tank. This is the best system, because your pump will never feel a restriction and it won't shorten the lifespan of your pump.