Better late reply than never
I ended up buying a new build (AMD Kuma 7750 setup) and the KK266+ is in storage (I'm nostalgic about old computer parts).
I send the video card to XFX for testing and found out it was defective and they asked me if I want the new PCI-E versions since they do not have AGP in stock (the double lifetime warranty worked great!) I got an upgrade for free.
But other than that if I had the non-defective version, it could have worked!
Did it work for you? I have an old kk266+ and I'm thinking about upgrading it slightly as a stopgap measure until I can get a a couple hundred more dollars to get a new system. I'm thinking about buying the ZUMAX 550w psu with the -SAPPHIRE 100175L Radeon X1650PRO 512MB- that you listed. I remember gettinga geforce 3 several years ago and had power down issues (when i shutdown the computer wouldn't shut off correctly and I had to hold the power button to shut it off all the way). That was with the old PSU though (only 300w).