Easiest Age to introduce new chicks?

[chickiepie]

I currently have 5 chicks, about 5 weeks old. I am really wishing I had bought a few more. Assuming I would be able to find more pullets to buy, (which might be kind of tricky around here) and I found ones of similar age, would they be easier to introduce to each other than older chickens?

 

[ChicksterJo]

As I understand it, yes because they would be roughly the same size. I was having trouble keeping my ~13 week olds from my 9 week olds and 2 week olds.