Well since Live 3 won't be AltiVec optimized, then using OS 10.3 Panther might provide a significant performance boost alternative instead.
Here are some posts from an OS 10.3 developer about the greatly improved performance of Panther including much more efficient Core Audio:
http://www.pstheme.com/cgi-bin/think/ik ... f=15;t=918
Here's a quote from the Think Secret site:
"
do you have any impression about how panther performance is on older machines, late G3/early G4?
I've tested Panther 7B28 on my G4/500 AGP with an Rage 128 Pro and now a 8500 (QE on). It is much faster, even non QE Macs will see a way noticeable difference; I should say especially non-QE Macs. My initial post on this thread explains why. Every Mac will see a major boost because of the code enhancements made to the system. As an example, on a 1GHz Mac, OS 10.3's iTunes playback now takes less than 1% of the CPU! OS X's improvements mean that every one of your Mac Apps will have a lot more processor time to themselves. For App that dynamically link to the public frameworks, they will notice an even greater performance boost."