I have a 75g reef with 1200gph dual overflow, one outlet is plumbed into my sump w/skimmer and the other goes into my refuge, both dump into a single return tank and the water is pumped back up to the display. I would suggest letting gravity do the work of getting the water into your sump and then pump it back up to your display. Just make sure that your sump isn't filled to the top or you could have a mess if the power goes out or your pump fails. A 10gal tank from walmart for about $10 with a bubble trap made of acrylic was my first sump w/refuge. I use it now as my return tank. HTH
and good luck!!