Yes, the IIS stream is exactly what goes to the DACs (you can configure it to be front/rear pairs or front pair plus sub (4th order lowpass) and centre (L+R mix) - this would allow you to get a sub out whilst still getting the 4 analogue outputs from the 7705.

The CS8405 should be able to be run in hw config mode, so that there is no wiggling of pins necessary to configure the chip. ISTR that you *may* need a 5v supply to the 8405, though they say it in theory works from 3.3v an errata noted that you had to run the output VDD supply from 5v - this is something we came across with the Rio Central design. The IIS power pads on the empeg main board are only 3.3v I think.

Hugo