You know, I actually think it's sad that the company calls that their extra large cage. I mean, it's perfect for rats, and a really decent cage for rabbits and guinea pigs, but the fact that they have to call it extra large because they sell so many smaller cages (that are considered 'properly sized') is just wrong. I think it should be their 'medium' cage and they should discontinue their small ones.
Anyways, you might just consider just adding your own levels and always keeping them in that cage, since it really can provide a lot of room if you use the space properly.