Keep in mind the 2006-2008 Mac Pro models used DDR2 ECC FB-DIMMs.(do not remember about 2009, but I *think* early 2009 is when they switched to ECC DDR3) Not exactly cheap, though if it has 12GB you have a head start.
Also, do not buy one of the clear Cinema displays with ADC unless you 100% know your card has it. No Mac Pro has ADC, and even the late 2005 G5 only has DVI(because they switched to PCI-E with that model). Any ADC display is ten+ years old anyway and no good for production with the CCFL backlights being so old.
That having been said, Apple has been shipping DVI on their towers since around 2002 or thereabouts so you have no worries!
The gimmick is that ADC carried the power for the display in the same cable as both display data and USB for the integrated hub. So just a single cable to plug in... except they had a separate finger on the AGP slot for power, and used then-unassigned pins in the AGP slot for USB or something. I am so glad they switched to DVI only.
Make sure the display has DVI. You can use any display you want, like a Dell Ultrasharp!
It might be time for your PC to have a display upgrade.
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