I am also using ATV and airplay on it to stream music from iTunes (Bacbook Air) and best solution I have found is ATV via optical to external DAC and than to amp.
Not sure with which part you have problem here? that should work for you fine plus you have onboard DAC.
The problem that I have is that DAC (MyDac) has only one optical input (ATV) and PS3 superslim has only optical audio out and TV has no analogue audio out also.... And I would like to get sound from PS3 to my R100.
The issue that I see is that external DACs tend to have one optical, one coax and one USB inputs and more and more new devices (PS3, TVs, ATV,...) come only with optical out and how to connect it all? And I dont want to use AVR any more, had it for years and came back to stereo amp.