A pair of kribs or any other group 1 Pelvicachromis will be fine in a tank that size with small tetras. You could also go with any of the easier Apistogrammas (though I find them harder work than Pelvicachromis as they don't live as long and aren't as tough IME), Rams (good quality ones though), Bolivian rams, Dwarf acaras, the smallest dwarf pike cichlids and many others.
Personally I'd go with one of the less common Pelvicachromis such as a form of P.taeniatus or P.subocellatus. Tough, colourful, interesting and unusual. Perfect cichlids IMO.