Is Multi-Channel audio and Multi-Soundcard the same option?
Are multiple sound cards required for running multiple Slim Device players? (linuxmce + squeeze[anything] pulls search hits for softsqueeze, squeezeslave, logitech media server, slim-devices, and about 30 others I cant recall offhand. I just want to use use Slim Device Squeezebox Players/emulators).
This may be of assistance with your initial issue of the sound card devices being detected in random orders on boot:
A multi-channel analog out (like on most Motherboards these days) can be split into seperate stereo outputs and used for seperate squeezeslaves. This split is configured in asound.conf, here is an example: