Alsa is one of the most difficult to work with interfaces. There are several ways to talk to the mixer but that should be handled at a pretty low level. The driver abstracts those issues from LMCE as near as I can see. I have used audio cards from motherboard level to the Hammerfall without problems in terms of the mixer. And you can create an .asoundrc file (look at this for guidance for each card that is supported http://www.alsa-project.org/main/index.php/Matrix:Main
). The format is as non-intuitive as any I have ever seen and many have complained about it.
There are also interactions between the players (Xine, Mplayer) and Alsa that need to be accounted for. Mostly documented in several places.
Linuxmce shouldn't need to get involved with this unless you want custom setups or autoconfiguration of special cards. Its possible with Alsa to have a number of independent cards and audio streams in the same box but LMCE's architecture doesn't really support that in one box. I suspect it would be very complex to manage even if not difficult to program.
I hope this is close to what you wanted to know.