Wow, that looks good...
I'm actually a little surprised that the lower cabinets can hold the weight of the upper cabinets. Particularly,since it appears that you have the LP's on the upper cabinets and the CD's...which weigh a lot less, on the lower cabinets. Are the cabinets attached to the wall in some way? Pleased to see this arrangement, as i am going to have to stack my Kallax cabinets in the same manner. Although I won't be using them for CD's, just LP's.
Nice looking collection, BTW.
Yes, it looks odd to have the light ones below, but I do not listen to cd's as often as I do listen to records. Not even one tenth I guess. The shelves are strong enough so it doesn't matter which ones on top. You can bolt them to wall (if you have a strong wall) on the insides of outermost corner shelves as that makes it stronger in case. I dont know about Kallax. These are expedit and I know Kallax has less wood. Does that make kallax less strong, I don't know.