Is it possible to have 3ch system (L, R, C) without surround controllers (G65 or 861)?

The system would be: HD621, DSP5200.2 and DSP5200.2HC for center.

I could use coax digital out from HD621 to 5200.2 coax input and get L/R channels (master/slave).

The second coax out from HD621 can connect to 5200.HC coax input (center speaker).

For volume and source control I can use MSR+ remote. I don't know if center speaker should be master or slave? Besides coax cables should I use Comms ports for control?

I wonder if this setup is possible?

Also instead of HD621 can I use Oppo player with vanityHD modification?

Thanks for any advice.

218|UHD121|DSP5200.2|Apple TV