haywirepc: I've not had the opportunity to read this full thread, but you booting into Amithlon using Kernal 3 or 4 in your Kernal partition with boot script modified, correct?
If not then your NVIDIA card probably will display garbage on the screen.
I can say that the card I just bought is working perfectly with my Amithlon set up, and that I've had no hassles.
For what ever reason, both of my towers are not playing friendly with AROS, but it did boot using the Native NVIDIA drivers, but I've not gone as far as testing any 3D games or what have you.
Anyhow, I second what Fish says. Amithlon does reward you once you work out all the kinks. I spent about a week trouble shooting it on both my machines, and now I feel that I (for the most part) have all the vital stuff down.