What are the dimensions of your 500 Gal?
Do you plan to attempt to create a ‘natural’ type environment that allows fish to establish territories, or do you plan to create the empty box stuffed full of fish look?
I have very little experience with the empty box stuffed full of fish approach and do not find such tanks at all visually pleasing, so I won’t share any speculative thoughts on this approach…
If you take an approach that allows fish to have territories and make themselves “at home” in the tank, Then no I do not believe 6 Oscars will do well at all in your tank.
I’m sure the tank will have ample length (8’+) to allow two males to establish territories out of each others line of sight, which would be fine. If you wish to keep pairs in the tank each male could have a female.
Beyond that I think you have ample space for additional tank mates, as 500 Gal is a huge tank. My suggestions against keeping a large group of Oscars in this tank is not based on the tank not being large enough, it’s based on the principal that Oscars are not schooling fish and we cannot change the nature of a fish.