i have one paradise fish in a 60g with some red-eye tetras.
its a bit of a stalemate; the tetras are too fast for him to really hurt but the tetras are also much faster at eating up the food. while this works out ok in my tank, its only because the paradise fish is the largest fish living in the top half. this wouldn't be true in your case with all those large cichlids and a paradise fish in that instance could easily be out-competed for food.
however, if you do decide to get a paradise fish anyways, then definitately only get one. male paradise fish are as aggressive as bettas if not even more so. i'm pretty certain that there would be altercations. if you can find 2-3 females, then they can live with one male, but it can be a bit tough identifying the sexes in this fish.