That is an interesting thread! Hopefully your requirements we're a bit greater than mine.
I'm looking at this waverp library as a way to proceed.
Interface wise as my signal is already digital I'm thinking I can ignore the mic preamp that is documented for the ADC and tap straight into an input pin. For file playback instead of going through the DAC that is included in the WaveShield I hope I can tap in at the SDI input to the DAC.
Crazy?