The last three pumps are good but they aren't enough flow for what I want. I'm looking for something around 3500gph.

dang.. you should really be thinking about a external pump if your looking for that sort of flow.

I would but I'm really limited to space outside the sump since my Ca Reactor and all it's components take up so much space plus I'd have to drill the sump too. That'll definitely be the plan for next time.

Is this pump for your return or your closed loop? If for your return from your sump why so much flow? If for your closed loop any way to mount an external pump directly under your tank using brackets?

It is for the return. I want to up the amount of flow in the display an extra couple hundred gallons or run a couple more outlets plus run a small line to a refugium above the tank. I have an Ampmaster 4700 running on a closed loop right now and I love it but it's an inline pump.

red devil pump on a google search came up with a penis pump,ruth this confuses me

HeHeHe!
Try this webpage
http://www.aquariumobsessed.com/
You have to go to the "shop" and then water pumps and then Red dragon. Maybe I'll have to try that google thing - did it say if it's reef safe?