Originally Posted by accordztech
I think you should consider that most canister filters work with gravity in which the filter has to be below the tank so that a proper syphon to deliver the water to the filter and the impeller pump can push it directly to the tank. If the filter is level to the tank in the dresser it may not funtion properly.
Absolutely not. That would be true for wet-dry filters. It does not apply to canister filters at all.
For a canister filter, gravity plays no role whatsoever. Canister filter is a sealed system with two siphons that precisely counterbalance each other. Regardless of how you place your canister relative to the tank, the system will work (as long as it remains sealed, of course). The filter's motor will not notice any difference, regardless of whether the canister is above or below the tank.
Now, to the original poster:
Using longer tubes might produce additional "drag" in the tubes, i.e. the pump motor might have to spend slightly more effort in order to overcome the viscous friction in the tubes. However, 4 feet is not that far. Moreover, Eheim filters typically come with 8 feet of tubing, meaning that 4 feet of tank-to-canister distance is the standard distance for these filters. As long as your tubes are relatively straight (no knots, tight loops or compressed segments), you should be perfectly OK.