The problem here is with jacks: the Sawtooth's speaker jack is a standard 3.5 mm, while later G4s (starting with Digital Audio) have a 3.2 mm Apple only jack for the Pro speakers.
After about a half day's research, I found that if you want to attach Apple Pro Speakers to the G4 Sawtooth, you should get the iFire or PowerWave adapters sold by Griffin a few years ago. But BEWARE -- these items are now scarce, and iFire can cost $100; PowerWave is now $150-$200.
Other people have "hacked" the Pro Speakers, as shown on this page:
http://www.applefritter.com/node/3904.
The Mac Cube speakers are similar and have a USB connector. But they must be plugged into a higher power USB port, such as that on the Cube, or the port on a Cinema Display. Apple recommends against using the standard ports on your computer or keyboard.
Since I have an acrylic 22" Cinema Display with the Sawtooth, I ultimately ended up getting Cube speakers, because they are close in resemblance to the Pro ones, and they can plug into the display.
Yet another option are Harman-Kardon SoundSticks, which have been brought back onto the market and coordinate well with late '90s, early 2000s PowerMacs. You can get these for $50 to $100, depending on if you buy new or used.