Mine has a big Super Pet Multi level home right now, Its pretty big, I can't remember the dimensions though, I really want to build a C&C cage! Looking at how big most of these cages are, the one I have seems tiny! Here is a link to a pic of the cage I have:
Amazon.com: Super Pet Deluxe My First Home (multi floor large, blue base 30''x18''x29''): Home & Garden
Is that a big enough cage? The only difference is, the middle level on the one I have doesn't have a hole in it.