Most people recommend at least a 55g tank, they tear up plants (I have aponegetons, dwarf sag, and valisneria doing ok though, java ferns would work too) I guess sand would be fine (not sure, I use coral sand, cichlids like digging) you need at least 2 females to every male, 3 or more would be better to split up aggression, along with lots of rocks and stuff (I use these tree stump decorations) I don't think you'd need a powerhead.
While I like mine, there are arguably "cooler" cichlids. I can't name them off the top of my head, but they exist....lol. Make sure you read up on them and make sure you want them, they can be mean little b@stards. You will probably have to keep just kenyis (if only to prevent hybrids, not to mention the aggressiveness) They will dig up your plants... thats why mine are actually attached to the decorations, lol. Except for the valisneria & sag (not sure the sag is doing too well), thats just buried normally. My male kenyi actually reburries them for me when he digs out his burrow due to creative plant placement...