Hello Well I have my second hand Mac Pro 2010 model, a Nvidia GTX 680 graphics card and 2 x 30 inch monitors. I am running 10.6.8, and the graphics card only supports 1 monitor. Bugger! I want to stay with 10.6.8. due to some legacy software I am using that is not supported above 10.6.8. Yes I can get both monitors to work under 10.8.3 ( I have tried it ) I have installed some Nvidia drivers specific to 10.6.8 but without success. What would be the best way to add the second monitor? the easiest option would be to add a second graphics card. Would my old XT1900 graphics card work in a Mac Pro 2010? Which graphics card would you suggest that is a, inexpensive b, does no put any addition power requirements on the machine c, I would consider drawing power from the second unused DVD drive with a suitable power cable d, works with 10.6.8! many thanks for any idea and recommendations I know I am being a luddite using 10.6.8, but the legacy software pays my bills.