What is the distance from the 185 to the 40b? Personally I would sell the 2 sumps you have, and get a large custom multichambered sump under the 55 or whichever tank you choose to put where the 55 is now. figure you will need at least 25 to 30gal when the tank back siphons, especially if you choose to go with a large return pump with a lot of plummbing. I have 2 tanks and a sump on a 300 gallon system with a 3.0 sicce as a return pump. My system will backsiphon 15 to 20 gallons depending on algae growth on the drains. Looks like a fun project..