Even without the interest of actual breeding, these fish haven't been kept until they've been kept in couples (this is when all the best character and color is displayed) so no matter how you look at it a mate is always the best choice for fish like this.
Otherwise you can mix and match any new worlds that aren't too aggressive - it's always a risk since cichlids are naturally enemies, and sometimes it takes some trial and error to get fish that will hold to the aquarium truce. The Parrot might work, though being massive and monstrous it will draw all the attention away from your Acara. Festivum is worth considering, or perhaps a Firemouth or Severum.