i went with 160kbs aac because i noticed a slight difference in quality and the file size increase was not that much. i use to strictly use 192kbs mp3. i have cambridge soundworks speakers connected to my imac and i use my ipod through my car speakers and feel that the 160 is a perfect sound quality, 128 is good too and honestly the only time i can tell the difference is when i sit and really think about it. as far as quality, i felt that anything higher then 160 aac would be just using up space on my drive, i would have 100 albums at good quality to excellent rather then 50 at excellent to superb... if i want cd sound then i play my cds on my sound system.