I tend to find in any cichlid tank that i have ran, the trick is to get one cichlid that is somewhat larger than the others......
for example in one tank, i have a colony of electric yellow labs, tropheous duboisi and a few alunacaras. Life in that tank was bedlam until i introduced a very large female livingstonii who would give chase to any aggressive fish in sight, as a result i dont have many problems with the cichlids picking on one individual as it is swiftly broken up by the much larger fish.......
Regarding catfish i would recommend any catfish from the synodontid family and a few others my faves are:
Syn. nigreventis (upside down cat)
Syn. multiplepunctatus (cuckoo catfish)
Syn. ornatapinnis (ornate cat)
Syn. Eupterus (feather fin cat)
Syn. flaviatus (sp.) (pyjama catfish)
Gold synodontis (sorry dont know scientific name, gorgeous fish tho)
any member of the doridae family
Angelicus pleco
Clown Pleco
Rubbernose plec
Any form of sailfinned plec
and the beautiful thing with this is that you can mix any of the above species of catfish with each other AND cichlids!
Good luck and let us know how ya do
As an intersting foot note i know you mentioned "bottom dwellers" try looking into the smaller species of oddball such as peacock eel and polypterid/birchir these are unlikely but excellent tank mates if kept right, and interestingly enough polypterus ornatapinnis (although too big for your tank) is a native to lake tanganiyaka........