Personally, I agree, just thinking of bigger fish and severums sprung to mind as they make a good size but not overly aggressive or skittish, perhaps brown acara would be a better call? How big do you consider big as there are obvious restrictions due to size of tank and filtration.
I don't mean big as in a pacu or oscar I ment something of decent size that will look nice in the size restrictions I have...I have a aquaclear110 for filtration
A stocking centred around 3 Leopard Bushfish? They should reach ~14cm and are about as big as something you can safely put in a 3-footer, as they are normally quite sedatory movers.