The driver you have there is not ATI's own driver - it is the community-developed one which only supports 3D acceleration on fairly old ATI cards.
To get 3D acceleration on newer ATI cards like yours, you need ATI's Linux driver from ATI's website:
https://support.ati.com/ics/support/default.asp?deptID=894&task=knowledge&folderID=27
To get 3D acceleration on newer ATI cards like yours, you need ATI's Linux driver from ATI's website:
https://support.ati.com/ics/support/default.asp?deptID=894&task=knowledge&folderID=27