I need a graphics card, that supports 10 bit color OpenGL buffers (used in Photoshop for example).
I've explored AMD's website and found this document https://www.amd.com/Documents/firepro-10-Bit-whitepaper.pdf . It's written, that the 10 bit support is only available for the FirePro cards. The document is about 7 years old, so I have following questions:
You would need a Firepro card as far as I am aware, any of the current range would work but you would probably want a mid or high end card if you are doing heavy photo editing etc.
You have to use a FirePro card with Adobe software. Even though Radeon cards can do 10 bit color, Adobe software will not allow it. As far as displays go, you're going to want to get one which allows for professional hardware calibration and covers at least 99% AdobeRGB with a very low error margin, you can't use some consumer grade panel with 8+2 bit color.
Agree with the folks above.
Radeon Settings and Catalyst Control Center (CCC) show the display output colour depth in Bits per colour/channel. This is to match the colour depth on the display for output.
Enabling 10 bit in Radeon Settings/CCC for consumer products will match the colour depth on the display for output, but the surface being rendered can be 6/8 bit and is dithered to 10 bit output if this feature is enabled.