For medium sized birds, within the 100-180 gram range, the A&E/HQ Flight cages aren't bad! They are 23" x 32" and 35" height? Plus a stand, which separates from the cage.
For larger cages and/or slightly larger birds (up to 400 grams or so?), I recommend the 32x23 playtop/dometop cages that are built as 'one piece'. You can take them apart, but the only removeable part should be the tray(s) and cage grate and/or playtop. The legs of the cage is part of the entire frame of the cage.
Think of the cage as what the bird will be spending at least half of his life in for several years, unless you upgrade! Once you put in perches, toys and dishes, it tends to get a little crowded... and the bird will be in this cage when he/she is sleeping, when no one is home and/or when no one has the time to safely supervise him!
When I think of bird cages, I try to picture myself in either a closet or a bedroom... and then try and think about the size of the room and what all I could put in it... I'd rather be in a large bedroom with a bed, dresser, computer, tv, maybe a minifridge to be lazy/enjoy at leisure, etc rather than stuck in a closet where I can't move around very well and there's hardly any room to put anything... and then to think about how many hours I'll be in this space for... well, a closet/small space doesn't sound very appealing!
