This is the 100 x 54 Barney cage on top of the 80 x 50 Savic Mickey 2XL (same size as the hamster heaven. The 20cm doesn't look much but gives a lot more useable space and floor area.
I am thinking a zoozone 1/standard duna multy would be a good upgrade - not too big not too small - if they are used to a smaller cage at the moment. But 90cm might be ok as well.
Attachment 49365