The fluval FX 5 gives you only 350 gallons of flow and uses 50+ watts, horrible. Canister are amatuer, sumps are proffesional.
Stack'en wont help, just gives you some wacky currents and high electrical bill. Also you cant use them with planted tanks, it will drop your oxygen and raise your nitrates to dangerous levels. Canisters have low flow, costly, and are not energy effecient. Plus they only filter, sumps build an ecosystem. I went sumps and never looked back.
As far as costs go sumps are cheaper to build, maintence, run, and replace.