Sure, JOASPHOTO. The GT120 is okay, but it's a little slow and you may not find that it meets your needs. Just so you know: you can't link 2 video cards together to get more power, but I'm sure you knew that already. Basically: you have two options: 1-find a decent Mac-compatible video card that will work with your 2009 Mac Pro, or 2: Find a PC video card that has been flashed to work with Mac. For what it's worth, your Mac pro can run El Capitan, if you can find it somewhere. Don't know why you're on Snow Leopard, but oh well.... .... so, back to the topic at hand. Your Mac Pro, due to it being older, won't have nearly the bandwidth and speed in that PCI Express slot. So whatever card you installi in there should work, but slower, but it will work nonetheless. I'd say maybe give the Sapphire radeon 7950 Mac version a go. 3 gigs of video ram, works in Mac and PC, and guaranteed to work in a Mac Pro of your vintage no sweat. I don't know what your budget is for buying a newer video card, though, but yes, that might be one way to get 4k out of your Mac Pro. there might be newer video cards out there, but I don't know if they'll work with your Mac Pro or not. If you decided to go the flashed PC card route, that could work, but you'd probably have to have El Capitan installed first. Although the card might possibly work in your Mac pro without it being flashed, you wouldn't see a boot screen ever, until the video drivers had loaded, so, should you get into trouble and need to do some diagnostics, eg booting from the Recovery Parttion, you could be right out of luck on that one. hence, needing to get the card flashed. I'm sure there may be someone in the UK who will do that service for you...hope I haven't confused you too much...
John B
