the FireGL X3 works now?!
where there any specific steps you had to do apart from the non free and radeon.agp stuff?
also can you post a glxinfo -B output please?(note the capital B)
I had it working,stock xorg config, and radeon.agpmode=-1 but now it just stuck at blackscreen after init of login manager(lightdm) & X.
You can try disable ATi acceleration via xorg.conf and change AGP Speed to 4x (radeon.agpmode=4). Maybe it works, I didnt try.
https://ubuntuforums.org/showthread.php?t=2339861