Fx5's arnt overkill for a 100. Like others have stated, with regular maintenance, there should be no problem getting years out of an eheim canister. I have a 2217 and will be honest in saying I don't maintenance it as frequent, but have never had one single problem, and I got it in November.
I have a 125 gal with an fx5, 2217, and a cascade 700, it's great, but the fx5 is well balanced on it, no vortex, yet it's not underpowered.
Fx5 all the way