Ah ha! Volca is a great example. That is exactly what we want. I think I might have one lying around somewhere. I'll try to take a look to see if I can figure out what their approach is and what kind of performance they're getting out of the single output. There are going to be many possible ways to achieve that kind of result. We're pretty much stuck with our ADAU codec for now so I'm going to try to figure out the simplest way to do it with what the codec provides and minimal extra hardware.
@Sonoptik I have a complete layout and BOM of a prototype design for this that I did a year ago or so, so I'm not starting from scratch. I need to incorporate some of the things we're talking about and make sure everything is current. I'm busy with another project but I going to try to fit it in in the next couple weekends or so.