A couple pairs would be good, and you could add some *smaller* species of synodontis cats, like petricola or luccipinnis, I'd say 4. Just make sure you have an outlet to sell the brichardi fry as they are quite prolific as stated by another member. Discuss it with your LFS, craigslist is another great way to sell fry. The synos will also help with population control.
Now if you like brichardi/pulcher/helianthus, there are other tanganyikans worth looking into. Shell dwellers are very interesting fish. Species such as neolamprologus multifasciatus, brevis caudopunctatus, callipterus, meleagris, specious, similis, ocellatus, etc. As long as you do a good sized rock pile on one or both sides, with the shells in the open area, you can actually add other tanganyikan species, such as julidochromis species (marlieri, dickfieldi, regani, transcriptus, etc.), n. leleupi (hit or miss, can be pretty nasty, but can be laid back), altolamprologus calvus/compressiceps (the a. compressiceps "sumbu dwarf" is my favorite), or my personal favorite, goby cichlids (three genera: spathodus, eretmodus, tanganicodus). Just a though. This route will be more expensive to stock, but personally is one of my favorite kind of tanks. Tanganyikans just exhibit some of the coolest behavior I've seen in fish
