I don't understand the benefits of having a closed loop system over a sump system.
There are many reasons why you would want a closed loop over a sup.
1) The number of gravity fed overflows needed to drain the amount of water you can move through a closed loop is very expensive.
2) Many people have flow requirements for their sumps, IE; you don't want 1600 gph
, going through a refugium sized for a 55g tank Or through a wet dry for a 55g tank.
3) Closed loops don't flood
If you feel it is best to put that much through your sump, then I would hypotosize, you really don't have need of a sump and can get by with a closed loop by itself. Your skimmer will have a difficult time removing organics from the water with that much flow through the sump, the heaters will be ineffecient. Most of the things you put in a sump need dwell time to operate efficiently.