I've had OS X 10.6 on my iMac since i purchased it. It's currently on 10.6.8. I need to update to 10.7 in order to use some music software, but when i view the App Store, the only option seems to be Mavericks. Multiple issues have been reported with Mavericks and several of the music programs i use, so moving to that OS isn't an option. How do i update to 10.7 or 10.8?