Introducing a second cockatiel AND new cage?

[Cockatango]

I currently have one cockatiel in a cage that's the minimum size for one. I'm thinking about getting her a companion, and if I do, I'll obviously need to get a bigger cage.
My question is, what order should I do this in? Should I let the second tiel settle in the new cage and keep Tango in the first? I'm worried this would come across as Tango invading the new one's territory. Would putting them in the new cage with a divider be better? I'm stuck - please help!

 

[iamwhoiam]

If you get another 'tiel you will first need to quarantine that bird from Tango for at least 30-45 days so they will need to be in separate cages. Why not get a bigger cage for Tango and then clean up the other cage and put the new bird in that one at first. It is possible that Tango and the new bird won't get along so caging them together may not work out.