Zx20 Workstations & NVIDIA Quadro compatibility

Are there Z420, Z620, or Z820 users reading this that are successfully running Win 7 64-bit OS with a Quadro M6000?

I currently have a Z820/Quadro K4000 combo for Maya modeling and rendering. I have a 1125 watt PSU. The QuickSpecs for the Z820 list the Quadro K4000, K5000, and K6000 as "compatible". However, I want to upgrade to an HP Quadro M6000 but the QuickSpecs for it say:

COMPATIBILITY

The Quadro M6000 is supported on the following HP Z Workstations:

- HP Z840 Workstation

- HP Z640 Workstation

Is this because,

1. The M6000 is compatible with a Zx20 but HP doesn't have the resources to test it and certify it, even though the card is $4500 right now on the HP online store?
2. HP has tested it, and the Quadro M6000 is not compatible with the Zx20 workstations.

Thanks all!