I have an iMac with a 160GB HDD. As my iTunes library increased in size I got concerned. I have it duplicated on my MacBook and put a 500GB drive in the MacBook. However, making that update to the iMac was a bit more complicated. I bought a 500GB external and use it for media files, including iTunes. I haven't noticed any difference is the play, so I consider it a satisfactory upgrade, cheaper and a whole lot easier than install a new HDD in an iMac.