I have the biggest Midwest crate, too- the metal tag on it says it's the Midwest 2000. It was great when Earnest was housebroken, but not reliable about destruction.
I got it at the Boulder Humane Society, they have a store that sells used training equipment. $50! Craigslist and Freecycle are also great places to find things like that, I got 2 6X6X6' outdoor kennels for free, and an 18X6X6' one really cheap, I put all the panels together in a big circle for a play yard for the boys.
Just a tip, for the big wire crates, I reinforced everywhere the panels came together with cable connecters, and put two big carabiners around the wire in the place where the tray slides out so it couldn't move. Just a little extra safety.