stackable cages??

hey all, i have recently bought three hoggys, 2 females and one male. i have absolutley fallen in love with them and we plan to get another female in the future. Obviosuly though, more animals mean more cages and i was wondering what my options were? i have seen some of the cube type cages and i like the idea of flexibilty but ideal, well, i need something stronger. I love the idea of a stack of cages. Does any body have any suggestions or ideas to help me along?