AFAIK two cards could work - it should give audio on one of them- whichever gets as alsa default device....
I have two sound cards in core on Pluto just plays on onboard one, the other is used for additional stereo outputs, but not under Pluto.
Try with to see what devices are in your system with :
aplay -L, aplay -l
and try to change mixer settings with alsamixer (I think with -c n you specify to which card to apply)....