I was having the same problem and google was making me come here.
Well adding alsa in /etc/rc.conf, is not enough.
I now have:
DAEMONS=(syslog-ng network alsa netfs crond gdm)
the trick is to set the volume right, then open a terminal with applications/accessories/terminal, then use 'su' to become root.
Well you did set a root password at installation, did you?
before you do the next command, you are supposed to have done:
#pacman -Sy alsa-lib alsa-utils
#pacman -S alsa-oss
Ok, THE trick is mostly this:
#alsactl store
that create '/etc/asound.state', the current volume settings.
That's what alsa in DAEMONS line in /etc/rc.conf will restore!
Ok, I did not found all this by myself, I give credit to:
ArchWiki :: ALSA - ArchWiki
Hope this will help the next one, as it did for me.