Yeah, the fish you listed would eventually out grown that tank. Exodons would be cool. There is also a piranha called pygopristis denticulatus that doesn't get too big and can school even with silver dollars. There are other options if you're looking for carnivorous predators that are not cichlids. Datnoids for instance are slow growers that will eat other fish.
However, when they're full grown, they have a tendency to jump around, and bang in to things. A full grown oscar in a 55 gallon is going to do a lot more damage to himself, and things around him than a full grown oscar in a 75, 90, or 125 gallon tank.
1 of the following cichlids...
Flowerhorn.
Green Terror.
Jack Dempsey.
Texas.
I.E. the smaller sized cichlids up to around 10"
and there are loads of non cichlids you could keep.