It's a lot, but shouldn't be too much. I have two 1050s (equivalent to 4000lph) and they work great; granted my tank is a bit taller. How much room is there from your sandbed to your waterline? How are the PHs positioned? Tank dimensions?
It's best to have 1 on the side half way up aiming up towards the center of the front glass, and the other PH being about 3/4 the way up (on other side of course) aimed for the same spot. By aiming them up and at each other, you're going to get much more surface agitation and water turbulence on the top of half of the tank (ideal SPS
conditions), and calmer waters below (polyps, nems, etc.); this should eliminate the sandstorm.