The more room you can give them the better, but.......the last several years we have kept 1 cock and 5 hens in a 12 x 12 (144 sq. ft.) without any problems. They were all raised together from juveniles which probably helped decrease the chance of problems plus the fact that there was only one male.
i have a red gold male, a yellow gold male, both there hens, and a juvi red male in my 4x4x4 cage for about a week or so now as there new pen is being made and the old one had to be torn down.
they get along great, which has really surprised me!!! the juvi is getting restless though, he needs his room to fly and explore.
Both pairs and older and much calmer so they dont seem to mind much...plus they get alot more attention from me since i feel so bad for having them in there.