My 70 lb. female has a 42" Midwest wire crate. It's VERY nice and it gives her room to stretch out. The next smaller sized crate could fit her, but I just don't like the fact that she can't really stretch out in it, and she can't even sit up straight in the next smaller size. I only paid $65 or $70 for my Midwest crate from Dunn's (free shipping to boot!).

I've also got a 42" plastic crate, but because of how plastic crates are shaped, you really don't get that much floor space in them. So the only time the plastic crate is used is when she's sleeping in my room where the plastic crate is kept (with the door taken off).