I respectfully disagree, angels get to be large, too large for his already mostly stocked tank. The DG probably would not like all of that activity up at the top of the tank and the tetras might fin nip.If I was you I would not add anything unless it were a pair of dwarf angel fish or a dwarf gourami. not sure how big the tetras are but i know the zebra danios are quite small and remain at the middle/top of the tank. if your other fish are same than two small angels would do fine as they stay at the middle to bottom of the tank for the most part.
This all depends on you filtration though.
Your welcome!Thanks NMFishman! Love those P-51's!