I have two GCCs and I've found that cages run out of space for toys and perches/etc pretty quickly. So, yeah, bigger is better. I dream of having an indoor aviary, but just don't have a place to put it at the moment.
I have a flight cage from Amazon. Actually bought a double wide flight cage. If you have the space, these are great and give lots of room for toys without becoming crowded. Currently I only have one of the flight cages set up (not both for the double wide). The wheeled stand is awesome too for easy cleaning. I also have an wrought iron A and E Victorian top cage on a wheeled stand.
In my cages, I've been able to make use of some of the wasted bottom space by putting the food and water dish down lower. I purchased separate stainless steel dishes for my one cage (the flight cage) so that I could place the bowls where I wanted them. The cage had openings close to the top for the provided plastic dishes and that's just too high for my birds to use all of their cage, plus I wanted stainless steel. I do place a favorite perch up higher though so that my birds can go up and chill out in a comfortable spot.
Place perches on varying levels throughout the cage. Don't place one perch directly above another, cause the bird will poop all over the bottom one. Also, perches don't need to be perfectly horizontal. Trees aren't. However, I have their top/resting perch horizontal, so they're comfortable sleeping on it.
Oh, another thing in cage design. Once you set their cage up, try to hang a few toys to provide a spot where the bird can kinda hide/feel more secure behind. When my female gets nervous or wants to be left alone, she'll retreat back there and watch us out through the toys. When she's more comfortable and/or wants to interact she'll come back out. This really helped her feel more in control and handle things better. I've done the same thing for my more confident male and when he wants to just chill by himself he goes up and behind the toys and I know to leave him alone. In other words, a bird should have "his place."
Alrighty, hope this helps. Cage size, my flight cage is 30 in. by 18 in. by 34 in. (Optimally this cage should be wider. Most quality flight cages are. I have another cage in the works, but don't have it ready just yet. My girl spends a lot of time out on a play gym too.)
My A and E cage is 26 in. by 20 in. by 35 in. It's kind of an odd size due to its design, but it works well for my boy. I have him out on a play gym (bigger than his cage) much of the day too.
Lastly, don't expect to set your cage up in one go and leave it like that. Once the bird is in the cage and you observe things, you'll probably end up changing perch and toy placement. My boy likes things one way, my girl another. By observing them and tweaking things, I find I've been able keep them from getting bored and provide adequate perches/toys without making it too easy for them. My birds gotta work a little. Gotta keep those birdy brains busy.
