If you plan is to purchase a new Mac, of whatever flavor, in the forseeable furture, I would go with Toast 9 as you will still be up to date when you move to it.
That said, your G4 Sawtooth can handle it without a problem. Note that there is no RAM requirements mentioned in these lists, which were taken from the Roxio site.
Toast 9 Specs:
Macintosh computer with a PowerPC? G4, PowerPC G5, or Intel
I was all set to buy Roxio Toast Titanium 9 online for my G4 Sawtooth Mac (and any Mac I may have in the nearish future) but couldn't find specs requirements beyond the Mac models that were accommodated, even at Roxio's own Web site. I phoned the place that was having a sale on Toast 9 and was told that I should have at least 512 MB of RAM for it. I have 384.
I know that sometimes salespeople are overly cautious about such recommendations. Does any of you have an opinion on this subject? And is version 9 (version 10 is out now) so superior to 8 that I should wait to buy Toast in any version till I have more RAM? For that matter, do I actually need more RAM to run that version of Toast if that is all I would be running when I burn a CD or DVD? For now, that's all I want it for. I have the capacity to burn them even now, but I gather that Toast does it so much better than the burning facilities of OS X (in my case, 10.4.11) alone.
I also wondered whether even version 9 is likely to become obsolete when the newer Macs and OS versions come out. It is my impression that there is going to be some kind of sea change in a shortish while, so that older software may not be able to be used.
So many questions. Thanks so much for your indulgence.