How is the water entering the sump? Is your overflow pipe coming straight down (i.e., vertical)? I've found there's not much you can do about the water crashing in that kind of case. You need to switch the overflow pipe so it can enter into the sump at some kind of angle (or at least have a section of gentle slope). This slows down the water so that it "slides" into the sump rather than "crashes" into the sump. I don't know if this makes sense based on my description. If you can maybe draw a rudimentrary diagram, or show us a picture of your sump setup right now maybe we can offer some more specific suggestions.
Don't worry, there is a solution out there.
