I want to use pulseaudio with this installation so that I can have multiple audio sources playing at once. For example, I will be using the Logitech Squeezeserver at the same time as MythTV is open in the background.

Mythbuntu 12.04.2 came with pulse installed, so I modified the /etc/pulse/daemon.conf to add:

default-sample-channels = 6

I also installed xfce4-mixer package to be able to modify volume levels if desired.