Thanks Knownothing, that was the type of answer I was looking for. I believe my weak link is my speakers. I tried a comparison with a classical piece (cd version compared to itunes plus), there was more dynamics and air on the redbook compared to the cd I burned with the aac file. The first test was "hard rock" which was quite a bit compressed in the first place. It was harder for me to tell a difference. The 256 acc, however, did sound quite good and if I did not have the original CD, would have been quite happy. I hope HD tracks keeps expanding...and hopefully, Apple will have lossless downloads one day.