As far as LW is concerned, OS9 is limited b/c LW runs on Java & java has been advancing far beyond the last available version of java for os9. LW has also recently stopped developing new versions for os9.

As far as upgrading to osx, well that depends upon whether you have it already on disk (or wish to purchase it) & whether your computer has sufficient ram. You can use osx from G3 upwards but it would be quite slow to run on any mac with anything less than about 450-500 MHz proc. It depends what you're using it for however.

As far as Audion goes, are you sure you dwnlded the OS9 version & not the OSX version. The os9 version is 'supposed' to be able to run on os8.6-9.

It sounds like you have Apple's Disc Burner.