instead of spending $100 on a canister, why not think of making a small sump, feed it with a pump from your display and have it gravity feed back. Let me know if this interest you and i will make one for you.
Are you planing on keeping fish?
how much space is their above the tank?
if your bio load is going to be small just water changes would be enough, but you could always make a separate chamber to house cheato, carbon, gfo.
Make sure the cabinet on top can support the weight. Remember it's roughly 8 lbs per gallon of water then you include rock, sand, and equipment in your sump.