I regularly run games + Teamspeak or Mumble with no issues. Slackware64 14.0 with CL Audigy. I don't don't have a ~/.asoundrc, rc.alsa is untouched. I did have some goofiness since my Nvidia GPU has HDMI w/ audio so I blacklisted that module. I set alsamixer up, use 'alsactl store'
alias snd-card-0 snd-emu10k1
alias sound-slot-0 snd-emu10k1
# Don't load HDMI sound from the Nvidia GPU card
The only "glitch" is that I have to start TS or Mumble after
starting any WINE programs if I want TS and Mumble to have audio in/out during game audio (weird WINE issue).
You can use 'aplay -L' and 'speaker_test' to find/test the output channels. Also, audacity is a good tool to see what channels are doing what. You will need to check the links provided earlier in this thread for software mixing if your C-Media chip has trouble or can't perform hardware mixing by default (duplex and/or dmix) (Its been a long time since I used anything other that Soundblaster or Intel audio in Linux).
You may also want to check out this: http://alsa.opensrc.org/Cmipci