Well, if anyone hangs around in the chinchilla, rat, or ferret community, I'm pretty sure you've heard of the Ferret Nation cage. If you haven't, well.. Here:
Ferret Nation Habitat Model 142 - Ferret.com Simply because I think you're missing out if you haven't. Chinchilla and rat owners had some problems with it(bar spacing), so the same company released the Critter Nation. With that release, they also came up with the Guinea Habitat and the Guinea Habitat. I think it solves alot of the "not being able to build" problems, as well as having a door built in. The "Plus" one also has a fitting lid. They look just like a C&C cage, are the same size as C&C cages, but they don't look so "DIY". What do you think? Are these cages better, on the same level as C&C cages, or do you see an issue with them? The Guinea Habitat "Plus" retails for $55, the Guinea Habitat retails for I think $40.
Guinea Habitat Plus