My MacBook Pro is a late 2008 2.40 Duo Core with 2GB of Ram, looking to upgrade the OS. Currently running 10.6.6. Usage is for storing, syncing and playing music files and internet radio, plus backup for when the PC crashes. I need at least 10.8 for Rdio, should I go to mountain lion, mavericks or Yosemite? I apologize if there are already some good threads on this, if so could someone point me in the right direction?