depending what your water parameters are (if your water is hard and pH pretty high) you might consider some of the smaller shelldwelling Tanganyikan cichlids, which are not overly aggressive.
a few more danios and bows should be it, and maybe a/some bottom feeder(s), like corys or a BN pleco or 2-3 khuli loaches, but don't get a normal pleco! they get too big.
i slowly added 13 rainbows to my 200 litre and my guys got a lot happier the third week when i added six.
That was my magic number with 2 males 3 females and a juv...
before that they would spar a lot and fight over plants and one guy bullied the other away from the females.
they still spar at 13 but they both display now without a problem even though i have one dominant male thats a little more grown up and big (he's about 3 inches).
Rainbows are definately sociable and need a nice school to be happy.