Keeping plecos with discus is risky. Pleco's have been known to attach to the sides of discus to suck off their slime coat (they have been known to do the same thing to goldfish). Many people keep plecos and discus together but it is honestly just an accident waiting to happen.
Rams are actually a good choice for discus tank because they actually prefer the higher temps that discus need to be kept at. If I remember right you also need to check into the different types of corys to see what temps each species can be kept at, some do better at higher temps than others. A school of cardinal tetras are also good with discus. They can handle the higher temps and the discus feel more secure when there are other fish out swimming. Rummynose and glowlight tetras are the other two species that do well with discus and can handle higher temps.