You can get dkms from fedora extras. I'm not sure why you're getting version errors with the libstdc++ package if everything is up to date.
If you haven't already, try using yum to sort out these dependencies. You didn't seem to be using the freshrpms repository in yum from the output above so try adding the following to a new file called freshrpms.repo in /etc/yum.repos.d:
name=Fedora Core $releasever - $basearch - Freshrpms
yum install ati-x11-drv
and see if it resolves anything.
If you've tried all this already, you could have a look at this messageboard
for more help.