Gulp, I'm sorry to hear about your Oscar. He was a great pet, and it must have been hard to lose him that way.
You may want to consider getting Uarus. They reach 10-12", are gentle, and act more "natural" than Oscars. You could get a 5 or so small Uarus and let them form a pairs, and keep a male/female combination. Contrary to what you may have read, they are easy to sex. They can also be kept in a community tank with Cardinal tetras, corys, geos, etc. Of course when the Uarus get larger, the cardinals may end up as snacks depending on your Uarus temperment.
Good luck!