Welcome to freshwater Konrad! African Cichlids are very beautiful fish. Since you are interested in Peacocks, you will want an all male tank. Females are drab whereas the males have the vibrant coloration. I advise against purchasing juvi's that have not obtained their coloration yet.
Additives are not needed in an African tank. If you are going to try to raise the pH, use crushed coral or limestone. They are both natural methods and will increase the levels slowly. Chances are you already have hard water with a relatively high pH, correct? If not, just add the crushed coral to the filter. It's a set-it-and-forget-it method. About once every 6 months or so the bag will need to be replaced. I am not saying that the baking soda method is bad, it's just that it is alot more work and the results are instant. By using crushed coral, the pH is slowly increased and you don't have to dose at every water change.
I recommend having a sand substrate. Africans are diggers and will enjoy playing with the substrate. Make sure you choose a smooth sand, such as pool filter sand. It is heavier and will not get pulled into the filter when the Africans dig and spit.
Rock structures are a must. Hiding spots are required for the Africans to feel secure.
Regarding the Catfish, there are a few African catfish species that reside in Lake Malawi (if you are going for a pure Malawi tank). If I remember correctly, there is only one specie that is small enough for a home aquarium. If you wanted to mix the tank by using non-Malawi catfish, you can. If you are interested in the specie of the Malawi catfish, let me know and I'll look it up. I just read it a few months ago in the TFH magazine.
A great site for fish pics is
www.malawimayhem.com. They have some info, but the bulk of their knowledge is in the chat forums. The members really know their stuff.