I don't think your TV has two HDMI ARC outputs.

You can Group either/both Amps with the Arc but the Apm's speakers will have a 75 ms delay from the Arc.

You could use the entertainment Amp's speakers as Surrounds for the Arc with no delay but that may not be what you want.

So you want to use the four entertainment Amp speakers as surrounds? Are they behind you? For use as surrounds they should be.

​@106rallye - the 4 sonance speakers are ceiling speakers.  They will not be behind me but coming from above. 

I believe I can bond the Amp and the 4 speakers to the Sonos Ultra Arc although probably not needed to be honest.  I think the Soundbar alone will do the trick and adding a subwoofer down the road could be beneficial.  

Well, at least some of them could be (above and) behind you. As I said connecting the Amp as surrounds using all four in ceilings will sound strange with TV sound. Using them for music (either grouped with the soundbar or not) will be fine.

I just discussed this yesterday with a Sonos rep. he told me that the 75ms latency appears only at the start, but if the sound from the TV goes via e-arc to the amp, then there will be no latency between the amp output and the arc ultra. I am having the same issue, trying to expand from the arc ultra to an amp + floorstanding speakers / bookshelves, and I received this info that the latency won’t exist.

I don’t have any idea what “the 75ms latency appears only at the start” means, but it isn’t the truth.  Any room grouped (not bonded) with a TV source will be delayed by 75ms, causing an echo.  You can bond an Amp with the Arc Ultra to make them surrounds (bonding is a one-way private network used for low latency surrounds/subs) and there will be no echo, but they only receive surround channels. 

As to connecting both the Arc Ultra and an Amp to the TC, as above, I know of no TV’s that have more than one HDMI-Arc/eARC connection.

As I understand it, the Arc Ultra & the AMP have to be set up as different rooms. On the other hand, I just bought an Era 300 to connect to my turntable, and, from the same Sonos rep, I understand that there will be no latency between the Era 300 and the Arc Ultra, both playing the music from the turntable. 

Music will not be out of sync, because they both add a 75 ms buffer in order to stream reliably.  TV sources, on the other hand, need to be in sync with the video.  So a Home Theater (soundbar/Amp + surrounds + sub)  has a private network that connects the main component directly to the surrounds/sub.  This low latency connection is good for units in the same room, but it is not robust enough to go between walls and floors, which is why grouped rooms for TV sources forego sync and add the 75 ms buffer for a more robust connection.

​@alexgib Not sure what you proposed set up is, but if you’ve got an Amp connected via HDMI-ARC (the Amp does not do eARC) you probably cannot also connect an Arc Ultra to the TV - most TV's only have one ARc/eARC connection. So you’d have to group the Arc Ultra. With TV sound it will run 75ms behind on the Amp.

You will probably need to connect the Arc Ultra to the TV and bond the Amp as surrounds to prevent the lagging.

There is a 30ms latency between the TV HDMI-eARC and the SONOS ARC’s audio output. Most viewers do not feel this is annoying. The 75ms latency annoys most viewers. At the risk of annoying TV viewers, you may be able use the SONOS ARC’s TV Dialog Sync to improve the sync between ARC and AMP when watching TV — but this is likely to degrade overall lip sync. You’ll simply need to fuss with this. Success (or not) depends on the lip sync of the video source and your tolerance to any skew.