From what i had gathered the 'convert to AAC' option in iTunes would simply convert an Mp3 encoded file into mpeg4 so that, for example, a 5 meg file would be reduced to 4, that is, the converted file couldn't be greater in size to the mp3 file it was converting. not so. i just AAC'd an mp3 encoded at 64kbps and ended up with a file almost twice the size of the mp3. therefore: AAC must be decoding the mp3 i guess to aiff THEN encoding again. since [i'm guessing] the loss of quality of the 64kbps encoding will always be present, encoding a poorly encoded mp3 to 128 kbps AAC will only result in #1: larger file size; and #2: even less audio quality. Can someone please tell me i'm wrong.