I've had my xDuoo X2 for about a month now. I have an Onkyo E700M and E300M that I use with the DAP.
One really annoying thing about the X2 is that it lists directories sorted by the timestamp of the directory in descending order. I hoped it would at least display the directories in alphabetical order.
If you want the directory listings (Menu [button] -> Folder) to be listed in alphabetical order, create a new (temporary) directory on the CF card. Move all of your existing top level folders to that directory. Then move all of the directories back to the top level. Delete the temporary directory you created. Ta-daaa!
Leaving this here since 1) I can't seem to create a new thread. If i do can, I'm dumb enough not to find it.

2) for possible searchers that are annoyed enough to look for a solution.