I bought a clean 733 MHz G4 DA (256MB RAM, 9GB HDD, DVD-R superdrive, NVIDIA GeForce2 MX) three years ago for $300USD. I spent $75USD for a OWC 512MB PC133 memory stick, $75USD for a 120GB HDD (this model can only handle drive up to 120GB w/o replacing the drive controller), and $150USD for OS 10.4.6 and iLife '06. Totaled out at $600USD. I have had three good years with it. It runs OS 10.4.10 with no trouble.
A few slow points:
1. Handbrake takes 24 hrs plus to copy a DVD.
2. If I have more than ten or so browser windows open in Firefox it starts to slow down.
BTW: in normal use and even when playing Neverwinter Nights I have had good performance from the NVIDIA GeForce2 MX.
I have been questioning myself whether or not it is worth to put any more money into this machine.
What I would like to do:
1. Add firewire 800 (it now only has 400)
2. Add USB 2.0 (it now only has 1.1)
3. Add a SATA controller
4. Add about 500 GB of drive space
5. A faster superdrive (mine burns DVD-Rs at 1x)
6. A better graphics card (a 9800 pro would be my preference)
7. Put in a dual 1.6 GHz processor module
8. Max out the memory
This will cost big bucks. I am really not sure it is worth it compared to a macbook or a low end Intel iMac.
See ya,
David