If you really want to go with a lot of different specimens I would recommend going with smaller peaceful species. If you want to witness breeding behavior however, keep in mind that nearly all cichlids get very nasty while breeding and stock accordingly. Also find that even my "peaceful" Keyhole is not especially fond of other fish, especially bottom dwellers, near his home...but will allow rams to hang around with it. *shrug* I'm not suggesting that all of these will get along together, but here are some interesting suggestions. Warning: some of these may be hard to find:
Mikrogeophagus altispinosus aka. Bolivian Ram (approx 8 cm) - Not as colorful as German Rams, but hardier and I love their "red trim"
Biotodoma cupido aka Cupid Cichlid (approx 13 cm) -
Mesonauta insignis aka Flag Cichlid (20 cm) - search by scientific name, sometimes shares a common name with a dwarf species
Nannacara anomala aka Golden-eyed Dwarf Cichlid (8 cm) - looks a bit like an Apisto, but is more forgiving of harder water
Cleithracara maronii aka Keyhole Cichlid (9 cm) - very peaceful (although mine is a little territorial)
Archocentrus nanoluteus aka Panamanian Yellow Cichlid (10 cm) - not SA, but supposedly very peaceful
Laetacara dorsigera aka Red Flag Cichlid (7 cm) -
Laetacara curviceps aka Dwarf Flag Cichlid (7 cm) - (if you find someone that sells these let me know!)
Archocentrus sajica aka Sajica Cichlid (10 cm) - Herbivorous, forms a territory around a cave, (costa rican)...unsure how compatible with other cichlids