Currently Being ModeratedNov 10, 2012 3:59 PM (in response to petriguna)
You don't need the the old DVDs, only the latest one. But as proof that you owned an older version, you need the Logic 8 serial number.
Currently Being ModeratedNov 11, 2012 6:53 PM (in response to petriguna)
As you are installing from the L9 DVD set... The Logic 9 Installer will ask you for both your original L8 serial and your L9 upgrade serial. You will need both serials to start the install.
Finally, as you are now running Mountain Lion, as soon as you have installed L9 you will need to use Software Update to update Logic as the original L9 version will not run under ML.