There was a vaguely similar thread on Sony TV and HDMI (I didnāt want you to think you were unique) .
A degree of the thinking was this that this a digital to analogue to digital to analogue problem .
All I can say is that I feed my Sat Dish with an optical and my blu-ray with a co-axial into a small DAC and keep it as simple as possible.
Optical adds no more processing steps than using hdmi. They are both digital outs and will go through the DAC in the Atom.
As for not powering on the Atom, hdmi-cec control is a bit flakey at the best of times on any TV I have had with any amp. Itās a lottery if it works as all manufacturers have their own spin on it and work better with devices from same manufacturer. Not sure what can be controlled on the Atom by HDMI as I use optical myself as I did not have hdmi Atom.
I have Uniti Star with HDMI ARC to my Sony UHD. When switch on TV, Star will briefly have sound and then disappear. I have to do the dance of switch off the Star again, wait for 2 seconds, then switch on to have connection. This whole HDMI ARC thing does not really work out of the box.
I have since moved to NDX 2 and using only Optical and it works every single time. But I know using TV remote to control volume is too good to give out.
The volume up and down is great, itās just frustrating that the amount doesnāt come out of standby and select HDMI input. Not really that difficult for the TV or Amp manufacture to facilitate. Given most audio and tv shuts down when no signal canāt be difficult to reverse the logic surely ?
If the HDMI ARC is supposed to be universally used again all sets should then work !
For me itās not a major issue but partner is fed up with all the damn remotes and switch this on, select this button, turn this up etc etc
I actually still use the optical, since the cable is way thinner and more flexible. I have the TV on a small movable ācabinetā, hence the preferred long and flexibility/agility of the cable.
I did once try the HDMI-ARC with my LG (from 2011) and it worked pretty well: volume control and within reasons detection of the input getting active/inactive. (So, if it were fixed, Iād maybe change to HDMI. I also put the Atom into deep sleep often; then I anyway have to power it up manually.)