I think I saw this concept already in the Blog section:
ADAU1452 SigmaDSP + 4/6CH DAC + 2CH ADC
... and additional SPDIF/I2S as possible extension.
This is something I am currently working on, since I would like to build my own fully active 2-way loudspeaker system. One would have the freedom to choose any power amp.
If this is something your working on as well, I would would be highly interrested ;-)