Okay update on the 5.1 multichannel analog output.
You can enable multichannel audio by creating an advancedsettings.xml file and placing it in %appdata%/XBMC/userdata.
The file needs to contain
But the problem is that the channel mapping is all wrong. My center channel is coming out of rear left, rear right has nothing, fronts and center are outputting stuff but not the right channels. Now I need to figure out how to remap the channels......