A way to simplify is to make the sump into an above the tank dump filter. Instead of overflowing water from a sump down into a sump and pumping with several feet
of head back into the tank... You simply pump water from the tank into a sump (rubbermaids) sitting on top of your tank and allow gravity to return the water to the tank via holes in the bottom of the sump.
Apart from not having to dork with diy overflows, you get a lot more flow out of your pumps. Pumping 1 or 2 foot or so into a dump filter will give you much more flow than pumping up 5 feet from a floor level sump
Matt