I'd either do a group of 8 'Geophagus' Tapajos Orangeheads, two pair of Laetacara sp. Bucklekoff, and two pair of Crenicichla regani 'Tapajos' and a huge school of lemon tetras ...
or
a large group of say 10 bolivan rams, two pairs of Laetacara dorsigera (or one pair and a trio of apisto's: borelli or mamore) and two pairs of Crenicichla regani 'Mamore' with a huge school of black phantom tetras.
For bigger fish I'd do something like a pair of Aequidens patricki, a pair of Crenicichla proteus, and a pair of Tahuantinsuyoa macantzatza with a large school of bleeding hearts or diamond tetras.