A big thing to remember with a sump is the drain-down that will occur during any pump/power outage. A 96W x 24D tank (height doesn't matter here) hold 10 US Gal
for each inch of height. The formula is this:
(Width * Depth) / 231 = US Gallons per Inch Height
---> there are 231 cubic inches in a gallon
The overflow in the tank will keep the tank water level a certain height above the bottom level while the pumps are running (the higher the pump rate, the higher the water flowing over the overflow). When the pump stops this water will continue to flow through the overflow until the tank water level is at the bottom of the overflow slots.
Let's say at your setup's flow rate your tank level runs 1/2" high, during a power outage the tank will dump an extra 5 gallons into the sump. If your sump were a 55G tank, (2.5G / inch) the water level in the sump would rise 2 inches. Since most sumps have separate chambers and spill-overs your 'sump' area likely is going to be half or less of the overall sump tank. This means the extra 5 gallons would raise the 24" x 12" sump by 4 inches.
Just something to consider as your figuring things out. I have a much smaller freshwater sump setup for a 30G goldfish tank, the sump is only a 5G tank! Since I didn't need a skimmer or refugium, the sump tank didn't need to be nearly as big as a similar marine setup. I have a filtration section (8" x 3", 7" high) with course and medium sponges followed by 3" deep filter floss for water polishing and a bio section (also 8" x 3", 7" high) with over a quart of seachem's pond bio-matrix. This leaves a 8"D x 10"W x 8"H sump section that holds 2.75 G. My 24x12 tank is 1.25G/in, and draining about a 1/2" adds less than 0.75G to the sump, raising it's water level about 2.5".
Just thought I'd introduce ya to the math of the sumps... it's really pretty easy once you know how it works! With a tank that size I'd look into using pond oriented filtration (like the pads & biomedia) simply because there's no real difference and it's considerably cheaper buying in the bulk!