i have ordered a sony nw a806 mp3 player and was wondering what format was best for encoding music. from my tests i have done i have concluded that AAC is better than WMA, however i cannot realy tell much of a difference between AAC and atrac 3, although i did think that atrac 3 sounded clearer at lower bit rates. i have asked someone else to do the listening test and they were able to constantly pick out between 160 and 192 kilbytes per second in AAC and WMA. they say that AAC is better than atrac 3 so i think i will trust them. also does the encoding software make a difference, the AAC files done with itunes are smaller than those of the same bit rate done with sonic stage somehow.