A better option for you is to stay with free radeon driver.
What are the advantages of the proprietary drivers?
I am speaking for those HD5xxx series onwards.
I had HD5450, the biggest advantage to use ATI driver is : 10 degC cooler, that is a lot for me, in order to keep it run much longer
Of course, second advantage is 3D.
For my ATI legacy cards, I stayed with Radeon driver for any Linux OS.
Save lot of troubles.
If you are really, well, really do not mind BSOD , breaking graphic etc, and if you are onto Debian, then read this on how to deal with Legacy driver installation on Debian Wheezy.
You need to understand how to use experimental repos.http://forums.debian.net/viewtopic.php?f=5&t=103918