play safe and give your fish a good home,meaning get a pair of oscars and nothing else,as for a pair of both oscars and a pair of jags in the same tank would sooner or later create ww3.
I think you could keep any of the following together...oscar, bocourti, pearsei, severum, uaru, chocolate cichlid. these are all fairly large growing but peaceful species. You could probably keep up to 3-4 of these but no pairs.
180 is easily big enough for 4 Oscars, and would give them enough room to show off their personalities and max out in size!! If it were me I'd stick to a species tank with only the O's, toss in some branchy driftwood, and wow...