i hardly ever use ati, but afaik ati-config will change your xorg.conf,
so i think you have to restart your xserver (sorry if this is obvious)
after running it.

here's an old thread about this:
http://www.rage3d.com/board/showthread.php?t=33851796

  

I also went through every FSAA value sent to gemwin between each
setting. None of these had any effect on the way text3d displays the
text. Is there something else I could do?
    

you don't need to play with the FSAA in Gem here. this is known to only
work with nvidia on linux.

the idea is to enforce FSAA from outside using the driver specific tools.

mfgasdr
IOhannes