Looks like a good cage with the top option, fantastic floor space! 
I don't see much problem with the inner liner height if it's 3", I have a 2 floor C&C cage set for my girls and the top floor tray is only 3" high. Haven't had any problem with that as my hedgies aren't climbers much. If they were, I doubt that a 6" inner tray height would do much to stop them anyways!
Don't be too scared of C&C cage assembly, it is a bit of a pain but not complicated and worth it imho
I don't see much problem with the inner liner height if it's 3", I have a 2 floor C&C cage set for my girls and the top floor tray is only 3" high. Haven't had any problem with that as my hedgies aren't climbers much. If they were, I doubt that a 6" inner tray height would do much to stop them anyways!
Don't be too scared of C&C cage assembly, it is a bit of a pain but not complicated and worth it imho
