Interesting thread.... Lets clear a few things up:
Discus may well eat Cardinals and similar sized fish, it doesn't always happen but it's normal if it does.
Disucs should be kept around 86F, most cories won't like the temp this high as they are from cooler waters. Research the any cory species your interested in with regard to temperature.
I wouldn't keep CAE or SAE with them, not worth the risk IMO.
Praecox Rainbows do not make good tank mates, they are far too active and fast for a discus tank IMO.
Angels aren't good tank mates either, unless you have a massive tank and raise them up together, then maybe it will work. More often than not the Angels will become more aggressive than the discus, beat them to food and generally bully them around, which can lead to stress/illness/death.