I'm just curious, Simon, what is your favorite species of anthias?
Fwiw lyretails don't stick together too often. Dispar however, stick to each other like glue. I had 9 lyretails in my 300 and ended up with 3 males and 6 females. Most of the day you would find one or two over here, one or two over on the other side etc. My dispar and never more than 6 inches away from each other.
Either way would work. If getting all females I'd get one slightly larger than the rest.