I have a 75 gal. reef tank with a 2 inch sand bed. Decided to put a hang on overflow to sump. Right now have a Penguin 440 hang on filter, Magnum 330 Canaster filter, and a Protein Skimmer. I am going to take it all of and run a 30 gal. sump with the overflow. I can't decide on what pump and overflow to go with. I am looking at the Mag 5 or Mag 7. With the height to the tank, the Mag 5 is going to do around 300 gph. The Mag 7 is going to do around 500 gph. The overflow is going to be a CPR aquatic CS90 or CS100. Now the CS90 does around 600gph and the CS100 800gph. The price difference is not that much, $10 for the pump, and $5 for the overflow. I am really stuck and have been trying to get this worked out in my head for weeks. Any input on this would be a great help. Tank does run cold and even thought about doing a custom sump that way I can get the biggest benefit. Thanks in advance.