Get a machine with a SuperDrive or buy Cleaner 5. That plugin you are referring to won't work on anything short of a G4 because of the reliance on Altivec. Cleaner 5 will be much cheaper than a new G4 with a DVD-RW drive, and will work on the older machines, although very slowly. MPEG-1 usually takes 1hr to encode 1min of video on my machine when I go for quality. MPEG-2 takes roughly the same time on my machine (although I don't usually tweak quality settings for MPEG-2).
Just noticed you DID have a G4... sorry about that. However, the plugin comes with iDVD or DVD Studio Pro. Obviously, since they both use QT to work with clips, they need to be able to export them through QT, so they produced the plugin.