As a follow-up, I downloaded the 15 day trial of Channel D's Pure Audio software.... very cool. It runs in the background of iTunes. You interact with iTunes, but iTunes is no longer in control of the digital stream to you DAC; it only serves as the database and user control interface. Bass articulation and three dimensionality were both noticeably improved immediately. I haven't played with changing the sampling/upsampling rates yet, but this is a no-brainer upgrade to anyone using iTunes/Mac for your source (not sure about PCs though). Just make sure to turn on the Isabella DAC AFTER the software is running, otherwise you just have to turn off and on again the DAC.