I am not sure if that would work. When people say that oscars need 60 gal per fish they generally mean past a certain tank size. It coudl work though. Maybe try to obtain a pair in order to be certain.
i would say one or two..simply because oscars need really high quality water ..pristene... they are known as messy eaters and big wastes depositors.. they are a great fish to own but require alot of qualtity care to avoid Hole in the Head disease. .. to grow up a healthy disease free oscar.. more room and less tankmates is the best way to go
Take it from the voice of experience 1 O in a 125 with some dithers and may be a couple of other small cichlids. Two doesn't work they just don't have the room and there will be aggression problems. A 180 would be much better for two if your looking for a pair start with six keep the two who pair up and re-home the rest (still no guarantee). I have a tiger O, a female jd, 5 sd's and a snowking pleco in a 125 and it seems to work well.
I'd say MAX 2, i wish you could keep more but a pair could/would form with more than two. Finding a single sex X6 is not only extremely expensive but hard and tedious.
So what i am doing because of that is getting fish that are "like" oscars like viejas, chocolates and sevs as well as a single oscars