Kribensis are a great all round species. Cheap to buy, colourful and easy to breed with. Another one to consider if Fairy Cichlids (or L[yretail Cichlids) They're quite plain, but very aesthetically pleasing with their flowing lyretails. Create some nice rocky caverns with some free swimming area and you will have a nice litte setup. I only have 4 at the minute, but if you had a group of say 6 fairies then i should imagine you will have a great group of them. Fairys tend to look after each others young, so say if you have 2 or 3 mothers in the group then all of the fish will look after the young.
As for something like convicts, then Jade Eyed Cichlids are a nice fish. A little different to the convicts, but they have been known to cross breed with each other, although you wouldn't want this to happen. They are prolific breeders. The person i got mine from had probably 200-300 young in the tank so just be warned. The problem with convicts which breed like rabbits is getting rid of the juvenilles once you have them!!