Out of curiosity, I have been downloading the Amarra Demo verison (based on enthusiastic comments made in a the sister forum run by Empirical Audio). This software exclusively runs on the Mac OSX platform. Th econsensus seems that its decoding algorithm leads to far superior sound compared to iTunes. The claims are true, in my experience. I have ripped CDs both in the Apple lossless format (unsupported till now by Amarra) and .wav files (supported by Amarra) and played them after each other using iTunes. The difference is amazing, and I will order the dongle right away to run Amarra without the intermittent silence that occurs with the demo version. Voices are more real, with plasticity and body, for example ("Live in London" by Leonard Cohen, released 2009). Actually, you it is hard to use iTunes after you have tasted Amarra.
BTW, I am using an Isabella with integrate DAC.
Bruno