Welcome to LQ
If you install aumix (it's on your Slack CD) you can use a file called aumixrc
However, I've found Alsa to be a bit easier with all this, and I use the alsactl restore feature (about every hour) and the alsactl store each shutdown.
When you install aumix you should (haven't used it for a while, you might need to check for man aumixrc) be able to browse man aumix and find the info.
If none of this helps you, please post back.