I wouldn't use them
I would sell the two canister filters. They will sell easy and will be great for somebody doing fish only or freshwater. The idea with reef is to keep nitrates at 0. Canister filters are NITRATE factories! Worse than bio-balls IMO. Use the money you get selling them to buy the biggest glass tank that will fit in your stand. Buy some glass and silicone and put baffles in the tank to create your own custom sump. Leave one area of the sump for your refugium. Buy PLENTY of live rock and fill the refugium with it as well as the display tank. The rock is NATURE's filter and that is ALL you need. You could save ONE canister filter, hook it up, BUT only turn it on when you feel you need a little extra mechanical filtration, 24 to 48 hours. Don't rush into setting up the tank. Take your time and do it RIGHT from the begginning and you'll save yourself money AND aggravation down the road.