I have a crew of 6 but may be adopting 3 more and need a big cage. The CN is too small for 9 right? Or is it 12? Anyways I don't like the book shelf grotto style cages because I can't hang hammocks elnless I hang hooks and I switch it up so that wouldn't work. Thanks, easy 10 points!

My favourite cage is the Ferplast Furet Tower. The only problem is the price - it's only available in Europe so postage internationally can be a killer. It was worth it for my boys, though. :) According to the rat cage calculator it can hold 17, but I only keep four in it. It would be ideal for your crowd, though. :)
Other options include larger bird cages, just converted to have small bar spacing, if you don't mind a bit of DIY. I hear Martin's Cages also provide some large cages, but as an Australia-dweller I'm not familiar with the brand. pets question and answers,www.5d2d.com
Try looking on eBay and Amazon to find some large, cheap cages. Look at the local classifieds for options as well - these are generally cheaper and sometimes come with extras. :) Ferret cages are usually ideal. Mine's a ferret cage but it perfect for my rather fat older boys (they are somewhat ferret-sized).
I hope this helps and you can find what you are looking for at the right price. :)

Rat lover
Owner of four with an enormous cage.

A sewer.

Do you have a single unit or a double unit critter nation? A double unit can fit 12 rats.
A double unit critter nation or a martins cage would be best.
http://www.martinscages.com/ If you get a martins you will want powder coated. Galvanized holds a pee smell and some rats will chew PVC coated. The pictures are old and the cages now have bigger doors.
Here is a cage calculator so you can see how many rats will fit in a cage
http://www.rattycorner.com/odds/calc.sht…