I have simillar question. 
I can't switch output from 1 to 2. I've got Sound blaster Live! 24bit external sound card and analog mixer ( Numark DM1050). 
I've tried with newest drivers  ( and without them too   

   ) .
I've tried to make my mixer work with another program ( but I dont like that program  

  ) and it worked properly.
In MixVibes configuration i have "device number" set on "2 (quad)".
I/ve checked speaker settings in creative and windows software.
That configuration ( mixvibes+analog mixer+SB) was working before reinstalling system.
I'm just out of ideas... help...