Talon is right, you can get away with the smaller cage to start with, then a larger cage, you can use the smaller cage later as a sleep cage.
Sounds like the second breeder is the one to go with, not just for the lower price but he seems to be more knowledgeable and caring of his birds.
This is my opinion, but you do what you think is right, whatever that is we are here to help you all we can.