Cockatiel Cages

Hi everyone. My mom and I were discussing getting a new cage for Piper. We would like for him to have a bigger, wider cage. I *think* I've heard something like, make sure the cage isn't TOO big for the bird?
Here are some pictures of his current cage.
http://www.imagestation.com/picture/...3/fadafab4.jpg
http://www.imagestation.com/picture/...e/fadafc45.jpg
http://www.imagestation.com/picture/...b/fadafd8a.jpg

What size cages do all the 'tiel owners have, and do you think we should get a bigger cage for Piper?
(NOTE: He is NOT in his cage all day. He only goes in when we're not home, or at nighttime.) :)

It looks like a good size for a sinlg tiel. But Im not a expert on them. PCB will know :)

Good Advice!

PCB, that cage looks almost EXACTLY like mine! Looks like the same size too. I am also asking because we are thinking of getting another 'tiel. I think he gets lonely when I'm away at school and nobody is home, so a bigger cage might be necessary. We're going to Petco today, and take a look at them. :)

Thanks guys! :)