I will have oscars, tinfoil barbs, and common plecos in this tank.
i would probably go with a single pleco, unless you are 100% certain of the species you are being sold.
when i bought a "common" pleco, i thought i was getting L. pardalis, which only grows to 10 inches.
instead, i was mistakenly sold a sailfin pleco" which grows to 18 inches and is intolerant of other plecos.
with oscars, tinfoil barbs and a pleco (or more) you will need heavy filtration as mentioned above.
honestly on a 220 gallon, a wet-dry system would be very well suited for the job.
if you havent already purchased your tank, you may check out whether or not you can order it pre-drilled...which would save you some work with your filtration system.
you can check out this article to see someone who built their own wet-dry, and it gives a good general picture of what you are dealing with
http://www.oscarfish.com/viewtopic.php?t=20620
if you prefer not to go the wet-dry route, you will likely need a couple of canisters and a couple of HOB filters to do the job on that large of a tank.