This is timely.
We had a request for a flashed Quadro K4200. Just yesterday I finished work on it. Drivers work beautifully, we were able to enable boot screens and all 4 GB shows up.
As a side bonus, having dual DP ports means the card can run a Dell 5K at full res and 60Hz.
I have not tried K2000 but seems likely it could be made to work as well.