Upgrading HP Z820 with Quadro M6000 or QUADRO RTX6000?

[Renderhouse]

I have the HP Z820 with two Intel Xeon E5-2692 v2, 12x 2,2 GHz. Since Keyshot supports also graphic render I'm considering to get a Nvidia graphic card. At the moment I have a AMD FirePro V7900, 2 GB, GDDR5  which is weak.
My problem is now that I don't know what graphic card will fit and run in my Z820 and also good for Keyshot.
I have the possibility to get a used NVIDIA Quadro M6000, 24 GB GDDR5X which seems to fit in there. But how good is this combo?
Better seems a QUADRO RTX 4000 or higher. But do they fit in my HP Z820.
Does someone have a similar setup.