A true canister filter is a closed loop system, so the water can be pulled by siphon from the aquarium. I personally would put the pump after the filtration media; the pump life will be increased if it doesn't have debris running through it all the time.
A sump system is open to the air, so a siphon will likely either pull too much or too little water. You would instead want an overflow box. An overflow box uses a siphon to bring water over the side of the aquarium, then has a baffle the water flows over when the water level rises above it. This allows only as much water to flow down into the sump as you have pumped up. The sump pump should be attached to the aquarium return line, to produce positive pressure for the trip back up. The sump pump inlet can be open in the sump or plummed to a bulkhead near the bottom of the sump.