Slackware and Debian are both more advanced distrobutions, neither come packed with the ATi drivers like you ask but both have their own driver packages that make it very easy to install.
I'd suggest Ubuntu, while it doesn't come with the ATi drivers preinstalled (or at least I highly doubt) it should be reasonably simple to install them via apt-get and Ubuntu is a GUI based distro, like SuSE, not like Slack or Debian
