Loving the aquascaping in that tank, awesome center piece for that room. If you don't mind leaving the South American biotype, a couple African Brown Knifefish would look stunning in your tank! Keep it up!
Eventually you should keep only a pair of firemouths, and perhaps add another laid back cichlid. One of the medium sized acaras, or rainbow cichlids
That's way too conservative, lol. He can have significantly more fish than that in a 5 x 2 setup.