And i need XGL to use ati's driver
Wrong, to use ATI's driver, you just need to install it and modify xorg.conf. You need XGL with ATI's driver to use fancy desktop effects. With the OSS driver, you don't need XGL for desktop effects. Which means that with ATI driver, you can have DRI, but not native eye-candy.
For the OSS driver, just try 'lsmod' in a prompt; and look for the radeon module. If it isn't there, look through your package manager to find x11-driver-ati (or something like that).