I read a few posts not many. I don't agree with adding them at all once, even in an established tank. It will effect the bio load, I'd recommend adding two or three at a time separated by a few days. You can totally add all at once, just test your water daily afterwards for ammonia spikes and the nitrite spikes. Be ready to do water changes.
Demasoni suck in my experience. They don't know their size and will pick fights with even large fish. In a group of 8 or so they calm down, but ya the can give fish hell, tearing off fins. Some other fish I would recommend.
Pseudotropheus socolofi or albino socolofi ( all white, really pretty)
Hongi island
White top (Or various) Afra's
Like the set up. Your going to love cichlids. Very personable, emotional fish. You can tell when they're happy, when they're pissed, and sometimes even when they're sad.
Good luck