And then for example aplay -D plug:p6 <soundfile> plays the sound in all speakers. In xine I have settings which produces original AC3 sound into all speakers by default (I've set nothing) if available.
I had no idea about how asoundrc files works, I needed to study it and went through /etc/alsa stuff to understand it. Now, the life with ALSA is easier :). Let me note, that I have an emu10k1 card (creative sb live!) with analog genius speakers.