Here is what I woudl suggest doing.
1. get the tank "reef ready". All this means is the tank will be drilled and have a prefilter installed. It will cost a little bit more that a bare tank, but if you stick with the hobbie it is well worth the investment.
2. The sump will need to fit under the stand so a 20 long should work out well.
3. Skip the canister filter and go with 1 to 2 pounds per gallon of live rock, a good skimmer and lots of circulation roughly 20x the tank volum turnover per hour. Canister filters are OK, but unless you stay on top of keeping them up they cause more harm than good.
TO set it up take the drain from the tank and pipe it to the sump on one side, place the equipment, heater, skimmer etc in the middle and have a return pump on the other side. I would suggest getting the sump drilled for a external return pump. This is just the basics. I do not want to give specifics because it will varry from setup to set up.
Do a little bit more research before you spend any more money. Take it from someone who spent enough for two system, but only has one.