I have to say my sevs are peaceful, great if you want a large fish in all honesty, but even then putting it in a tank with all those other fish you have is a big unknown I'd say.
The trouble with threads like this is that combinations of species react differently, 2 fish in isolation that are fine in different tanks may want to kill each other when put together...likewise, as mentioned, a species could be seen as harmless but you could get a particular fish with a not so nice personality from a different brood etc and it may be uber nasty...
I think the best chance you have at having a peaceful cichlid community tank keeping all the stocking you have is to go with something like bolivian rams or apistos just because they aren't too large and so if they are fiesty then the damage is limited. Also note you need to look at the required pH and temp etc for any new fish and ensure all the fish can co-exit in the same parameters just fine, and some cichlids will need a BIG tank so do proper research yourself! You never did say the size of your tank did you?
If however you are really into getting the most out of cichlidae in your tank you may want to re-home some of what you have leaving maybe only the catfish?
Just my thoughts...