If we get a Class C with an overhead bunk in front, I've got a ready-made "shelf", complete with windows, for bird cages. They feel really tight, though, unless they have a slide...and for the amount of space, it seems that Class A's of similar age and mileage may be the better value. The thing with Class A's, however, unless they are a bunk model which are rare, is that there is no space for cages! The only options would be to alter something else. We could keep the dinette area folded down, as if for a bed, cover it all with something to protect it, and put cages there. Or the same for a couch, especially a jack-knife type. Building a simple platform over the upholstery so it is stable wouldn't be much trouble at all.
From a financial point of view, these would make the most sense, since we already have a car to use as a toad. We could spend more on the rig itself, and buy newer/better...
This one, for example, would work well since there are already 3 seats (Pete and I would only use 2, after all), we wouldn't need the couch and could either remove it or build something over it for cages. There is a little counter space too...although not too crazy about the side-by-side fridge but not a deal breaker. And we'd still have the dinette for the bed, or extra surface area to use when I'm cooking and baking...
This coach, on the other hand, has a little more counter space, and I'd probably want to keep the sofa and use the dinette area for my parrots. Folded down, it would have plenty of space for cages, as I could stack the smaller bird cages...
Here, I'd use the open jack knife sofa I'd think...and I like the kitchen real well in this model...
I probably won't stop changing my mind about all this until we have the $ in our hand, find the rolling home we want, and pay for it! So be prepared for more posts like this one :).