2 of my bunnies are kept in a 2 wide x 4 long x 2 high with a 2 x 1 x 1 litter tray extension, plus a 3 x 1 grid shelf with 1 support for strength, plus a roof (bunnies will jump out otherwise - you may or may not want this). In total 40 grids. They also have an outside run which is about 4 times bigger, plus they get free range time inside the house. The C & C cage is for when I'm not here, and night times. I like to have it fairly uncluttered, as they like to do laps playing chasings, jumping up on the shelf and down again.
My two dwarfs are kept in a 2 wide x 3 long x 2 high with a 1 x 1 x 1 litter tray extension plus a roof, 29 grids in all. Instead of a shelf they have a cat scratching pole with two levels they can sit on with a cubby at the bottom. They time share the outside run and free range inside the house.
They all seem happy to be confined when needed, there is plenty of room for them to stretch out horizontally and vertically. I wouldn't advocate these cage sizes for a pair to be housed in exclusively with no outside run or free time, but as part of the whole package the cages are good. They are also a manageable size to clean.
Hope that helps!
