... with this solution?
Right, so the Egreat 10a arrived end of last week. I first tried connecting it to one of the hdmi ports on the receiver, a Marantz sr7008, just two and a half years old. No picture and no sound. After Googling and changing inputs back and forth it suddenly occurred to me that the receiver doesn't support 4k, so I moved the Monster cable to an hdmi port on the tv, an LG oled55c6v. That gave me a picture at least and I could go ahead and upgrade the firmware on the 10a. But there was still no sound when I played my music files via the vidon xbmc - not even through the tv's speakers.
Next step: fitted an optical cable from the media box first to the receiver, no result (probably because I don't know what button to press on the receiver's remote), then to the tv, no result, then to my Samsung soundbar. Worked yesterday, but not today for some reason.
Been attempting to set up a bluetooth connection. According to the setup page, the 10a detects a bluetooth connection between it and the soundbar - only thing missing is the sound.
It also found the tv, and asked me to type a pairing code, but it didn't say where to type it (nothing appeared on the tv screen like a little window to enter the code).
In the meantime I've ordered a Cablesson 4x4 splitter. That might help.
As a last resort I reduced the resolution setting on the 10a from 4k uhd 60hz to 1080p 60hz, and plugged the hdmi cable into the receiver. That produced a picture (of sorts), but dreadfully distorted, low volume sound. Not a good solution.
So that's how I've spent the first four evenings. Get there in the end, no doubt, only hope I live long enough :-)