Beginner Hardware Questions, ~here they come again~ Options

[Branch1999]

I'm just getting started, using Logic Gold on OS9.2 to lay out some midi tracks that I want to layer over with sampling, acoustic and electric guitars, and vocals.

~mucking about~

I'm using VST instruments and effects, laying notes down by hand, haven't saved up for a keyboard or sound card yet.
Around this point if I add any more effects or instruments I tend to get a message during playback that says something along the lines of "Mac AV overload- Not able to process sound in time"
Is this due to my soundcard? I've assigned more ram and it had no impact. (G3 450Mhz 500meg RAM) I know my system is getting a bit on the obsolete side, I've been spending too much time staring at the 1 gig dual processors... Should I consider a new system at this point or will my machine make it another year or two? Should I hold off on buying a new system in hopes that with the Emagic buyout the new Macs will come out with stronger soundcards in them?
Just looking for general direction before I go out and start dropping money (it's way too easy to do, even when you shouldn't be spending it)
Any help is much appriciated. Thanks!

[Synthetic]

yep... basically I think you are running out of processing power especially since you are using lots of plugs. More RAM might help a little but really you need a faster processor to keep up with all the data crunching from the audio and plugins. The only thing I can suggest without buying a new computer or upgrading your CPU is to bounce the tracks you have with virtual instruments to another track then you can remove some plugs and free up some CPU cycles and continue your work and adding more sounds. With a situation such as this... I also recommend not using any FX plugs until you have the whole structure completed... then start adding fx like reverbs. You may have to do the same thing with fx as the virtual instruments... bounce them to new tracks and get rid of plugs. You could also consider getting the PCI card they developed not long ago that adds more DSP power to VST apps which would help with that problem also. I am not sure of the cost though.