How much room do they need in the brooder? Cage? Help!

[Cheysr21]

I have them in a little rubbermaid tub and it seems to be getting tight. I have 4 chicks and they are supposedly 3 weeks old, so ... how much space per chick do they need at what age? I want to make them something a little bigger, or buy a pet cage, but I want them to be able to stay in it until they go outside to their coop.


Would these cages work?
http://www.petsmart.com/product/index.jsp?productId=2753342
http://www.petsmart.com/product/index.jsp?productId=3057123


I like this one because it's biggest, and tallest. I caught a baby sitting on top of the feeder today. I think they want to jump and fly.
http://www.petsmart.com/product/index.jsp?productId=3074864


Would they LIKE a ramp? Do they get bored? Can they climb up there, or is that a recipe for injury? I'm not handy with building things (I have no woodworking tools) so I'd just as soon buy a cage for them. Plus, I can use a cage if I ever have an injured bird, right?

I put mine outside when they are that age. They go in the coop with a heat lamp. Actually this year I didn't even give them a headlamp because they were so well feathered I figured they would be ok. (And they are) brooder in the house are a pain.