If I had that tank I would fill it with some of the fish that I already have lol. or I would try again with a group of texas and wittle out the females until I have a group of males again.
As others have said a definate no to the keyhole. The ellioti is also a no no with a texas. If you are going along the lines of an aggressive set up you want to try to ensure you get all male fish. The texas in particular get very agressive with females in the tank, no matter what the species. Jack Dempseys, although classed as agressive are not as bad as their reputation, they do get stressed quite easily and may just end up hiding all the time in an aggressive tank.
As for a ground crew, the geophagus Brazilliensis make excellent tankmates for the more aggresive set up, they are just as bolshy back and dont take any nonsense. Adding a plec with the mess they make to a tank of large fish will only make it hard work for you, you would need to be very strict on your tank maintenance. I would not recommend pictus catfish with oscars, although the net states they live together ok, my oscar managed to catch one of my pictus cats.
Oscars: these are a law unto themselves, as already stateg you can get a gentle one that can happily live with smaller fish or an outright monster that will constantly chase everything in the tank. It is not always the case to get a bunch of juvi fish and throw them in together and they will get on for life. Once some reach maturity that is when the problems start. One of my oscars lived with other fish for over a year without problems, then one day he went nuts and tried to kill everything, he now lives in a tank on his own.
The one thing I will recomend with an aggressive set up is that you should always have a spare filter and heater and tank available to remove any fish that start to get too agressive and attack others to ensure you have no deaths on your hands. This also comes in handy if any fish is injured in a squabble as a hospital tank.
Hope this helps
