I know people who have several oscars in large tanks, and they often do well together. Typically though, they seem to do better and have less aggression if there are only 2 in a tank, no matter the tank size. Each fish may claim a territory, true, but they'll also spend much of their time cruising the entire tank. They're going to come in frequent contact with each other. If you get all peaceful oscars, this won't be a problem; if you get one aggressive oscar added to the mix, it could be trouble. You can still get aggression with only 2 oscars, but in my experience, if there are 2, they will usually "buddy up" and spend most of their time cruising together.
IMO, put 2 oscars in your tank, and add some other large, SA cichlids for variety.