One reason you may not hear a difference is that the Mac sends everything to the Airport as Apple Lossless. It converts the AIFF file to lossless and then the AE converts it back to SPDIF for your Dac.
Thanks for that - I did not know this. I don't use iTunes for playing files myself. I stream them via Squeeze software to a Modwright Transporter. I assume they are not converted going this route. Thanks also to Kijanki - is "MAX" by the same folks who created EAC? I'll look into it. I was really surprised by the differences i could hear in the EAC files I compared with a friend. There were certainly subtle improvements in bass, clarity and resolution overall. Have you compared using this "MAX" software? I must have missed some threads or is this brand new?