Quartz Extreme will not work on your PowerBook, unfortunately.
There has been some confusion over Quartz Extreme, so let me attempt to clarify.
The requirements for Quartz Extreme are that you have an nVidia Graphics Card, or any ATI Radeon card. That means if you have a GeForce 2MX, GeForce 3, GeForce 4MX, GeForce 4 Ti, Radeon, Radeon Mobility, Radeon 7500, Radeon 7500 Mobility, or Radeon 8500, you can use Quartz Extreme.
Next, there is a RECOMMENDATION of 32 MB VRAM. This is not a requirement. Only the kind of graphics card is a requirement. So if you have a Radeon Mobility with 16 MB VRAM, you will still be able to use Quartz Extreme. This includes the latest iBook it WILL be able to use Quartz Extreme.
Unfortunately, you do not have a qualifying graphics card, since you only have a Rage 128 Mobility. This means that you will only be using Quartz, not Quartz Extreme. No doubt Quartz will still be a little faster, but you will not get hardware benefits.