I am using the VRM box, but having to use it on its own, rather than in conjunction with MR816.
I am running on a PC therefore you can only have one ASIO driver active at one time ,therefore leaving this set to the Y/S driver. (This might be different on the Mac?)
You can theoretically use SPDIF out of the MR into the VRM , but found this annoying as VRM software is not running inside Cubase as a host and everytime you make a change in the VRM window to change speaker smulation settings etc, it stops Cubase playing as you are clicking inside a different application hosted outside of Cubase.
I therefore tend to use VRM as a reference for mix downs already made - rather than making mix changes on the fly. I suppose it is giving you confidence that mixes sound good on a range of speakers rather than a reliable means of making mix tweaks in headphones on the fly.
It’s ashame that Focusrite have not implemented the integration properly with other apps but cant complain for the price of the VRM box.