So far I am quiet happy using the DAC+DSP board. As I am having an external DAC (provided by my Active Speakers), I only use the Toslink connections from that board and completely neglect the DAC part in the DAC+DSP board.
As my usecase going to more digital inputs, I am looking for more digital I/O in combination with the Hifiberry DSP. If I add more digital inputs to this board, would these show up as inut devices and handled by the DSP as sound source? Is it possible to get the all-digital boards to work with the newer DSP board?