budgie cage question

i have 2 cages for my budgies. i keep Picasso and Nipoleon in the big one.(18x19x13) and i keep Kirby in the small cage(15x11x8).

i know the small cage is REALLY small, but i use it for the sick birds. Kirby was too young and was ill when i got her. she's tons better now and needs a bigger cage. i don't really have room for another big one so i was thinking just adding Kirby to the big cage with the other two. i have their cages sitting right newxt to each other and they get along. is the cage big enought for 3 budgies?

The big cage is just perfect for two budgies, but I really don't recommend using it for three. They're sooo active (part of why I love them so much!). How about going for a cage in between? My measurements suck, but I think a 16x16x16 cage might be good. I read on a website that a bare minimum for a single budgie should be 16" cubed. Hope this helps!