My early 08 mac pro has an ATI Radeon HD 2600XT 256 mb card. My machine is has 2x2.8 Quad core intel Xeon with 10GB 800 MZ DDR2 F8 Dimms. I use it for photoshop and video editing. Dual op systems are 10.6.8 and 10.9.1 on second disk. I would like to upgrade to a video card with more ram. 512 or 1GB would be good. Any suggestions would be appreciated.