You have a misunderstanding of the system.
We do not use xine-ui.
We use a player that takes DCE messages, based on libxine.
This player code is in src/Xine_Player in our SVN.
When Xine_Player starts, a configuration file is created for the libxine thread, based on configuration of your media director thread. Now, you can go to wizard > media director and change the sound card to "Manually Configured" ... at which point, you can manually modify /etc/pluto/xine.conf and change the sound settings there...
But this is a band-aid, and if you do that.. then.. okay.. we can't really help any further.
What NEEDS to happen, is you need to look at our asound.conf to see how things are configured, and look at what needs to happen to have our system output the correct sound configuration, either via a device template override, or through core code changes.