I have several power heads in my sump. One creates flow for some frags, I have two pumps that power the skimmer and another that pumps water through a carbon reactor. They all help flow. It is not uncommon to have flow in the sump if you want to keep detritus suspended. Some people choose to have a very calm sump so that detritus collects and can be siphoned out.
You want to do whatever works best for your filtration system and maintenance schedule.