Alsa-base is a Debian package, and some of it's files and procedures of setting things up are Debian specific. I have run 2 different soundcards with alsa on TC, normally using alsaconf and selecting the card works. /etc/modprobe.conf and /etc/asound.state are the files that alsa stores it's configs in on TC.
For using the /usr/local/etc/alsasound script on boot, blacklisting the module of the card you do not want to use may allow automatic loading of the other card.
TC uses a modified alsaconf and alsasound scripts to work with our setup, but one should be able to set up alsa per the alsa docs on their site all the same if this doesn't work.