Well, I don't know of any 165 litre tank which will fit angels at all (height and length wise), and I have never heard of 4 angels working in the long term (they are aggressive, so should ideally be kept in groups of 6+, (breeding) pair is also ok, one on its own is poor but works and 2-5 almost never work), so it sounds like you have enough problems on your hands without more fish.
But as a general theory answer: yes, angels and SA dwarfs are compatible. The number of SA dwarfs depends on the footprint (bottom area) of the tank. The right balance between number of males, and males and females is quite important for most.
