Unfortunately 150 gal. isn't THAT much real estate for an aggressive community. I speak from experience - I used to have the exact same tank set up. Had two Oscars, a JD and a pair of Cons. It was in pretty much constant chaos. My advice would be to pick one dream cichlid & add a few dithers to add some action in the tank. A large cichlid will take over the entire 150 gal. as its territory as an adult, so while a nice community may work as juveniles, as adults it could come down to an all out war.