I don't remember any of the third party servers supporting hierarchical playlists. Even the Slim Server based solutions only supports them via the lame approach of browsing the server's folder structure.

You could probably make the slimrio code run on an empeg fairly easily, but then of course you would not be using the empeg's UI to access the server, which would make it fairly pointless.
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Remind me to change my signature to something more interesting someday