Hi

I'm not sure that I fully understand your proposed solution. Does the Oppo 103D convert the DD+ feed from the Roku into something that your 861v4 + HD621 can cope with - if so what is the codec that it outputs?

A possible solution might be to use a small NUC PC with Kodi and the Netflix add-on. Kodi gives some options for audio output and it may be possible to output the required audio stream.

Cheers
Tom

Main: G61SL, 218, HD621, 2*7200SE, 7200HCSE, M6s, DSW, Apple TV 4K, NUC (Roon server)
Secondary: Wiim Pro, 3200, Audio Core 200
F80