I have one male and eight females in my 180 gallon reef and they do really well as a group. I would not, however, add a male to your tank. I think you would be better off adding 2-3 more females. Anthias will change gender, but from female to male - not the other way around. If you add a few more females, one of them will likely change to a male - this is what happened in my tank when I initially introduced 12 females.
Simon