Your fish should be fine with African Cichlids, not sure about the guppies but the others should be ok with them although it does depend on which cichlid you had in mind... beware though that african cichlids do prefer higher pH levels and you need to check that agains the needs of the fish you already have. found this which looks quite good... http://www.timstropicals.com/Compatibility/NameResults.asp
Your basically looking for a cichlid that would behave itself in a community setting. As a result I would point you towards dwarf cichlids suchas kribs rams and the apistogramma genus. These fish stay small( a few inches in length) but still exibit all the same great colours and behaviour as their larger counterparts. I would steer clear of the africans and any larger new world fish, particularly if you are fond of your present stock. Good luck
I think if you make the right provisions that a pair of Kribs could be an interesting addition to your tank. Having kept several pairs, I can safely say you'd need to provide a home for them such as an upturned pot, weighted down to stay in place! Once they find their new home, they may be slightly boisterous as they establish "their" territory but will settle after a while. They are most interesting to watch as the male pursues his mate around the tank, not helped by her flirty "s-shape" dance she saves especially for him! Great characters, who as far as cichlids go, are reasonably easy going!