What is the Current Guidance on Stereo and AV Configurations

combo systems can work well and are real world solutions for sure.

personally i have two separate system in 2 different rooms. a dedicated 2 channel room and separate home theater with Dolby Atmos 9.3.6 speaker configuration. 

if you have questions about multi-channel speaker configuration here is the definitive guide for that from Trinnov, the experts.

https://drive.google.com/file/d/1qFpM5c9_n_0PU6EcW-J5qFvf4QDWqjg3/view

I've ran an Atmos A/V system for years prior to separating my 2ch setup from home theater recently.  My A/V system is still very capable for music, but my needs have changed. 

To answer your questions:

1. Yes, you can put together a world-class system that does it all.  Your restrictions are really only convenience, money, heat dissipation and space.
2. Personally, I think adding rear channels or height channels for Atmos makes a bigger difference than 2ch versus 3ch.  Some speakers are better for this than others.  With full-range speakers, you can easily get away with 2ch.

Not sure if any if this is relevant for you, but a few observations:

• There are a few A/V Receivers that come with XLR inputs and outputs.  The Yamaha RX-A8A is very solid and a great way to add a dedicated amp.  You can also add a dedicated DAC to its XLR inputs, if desired.
• eARC implementations vary across manufacturers and bigger manufacturers will have better compatibility.
• If you're ok with a 2ch setup with HDMI inputs, there are a few options, but not many.  NAD M66 comes to mind.  There are likely much more that will come out as the Chinese DAC manufacturers have even started adding eARC inputs (which is another configuration option).
• If you're set on keeping your speakers, you'll likely achieve the biggest sound quality gain from adding in a good dedicated amplifier than spending more on a receiver/processor.

Soix, it's just the two of us so we're generally should be okay. We have however found that the mix is such that music significantly impairs the vocals. I take your point about the subwoofer but it may be a step too far for the aesthetics.

Pynkfloydd, yup, I'm using ARC into the NAIM today and that's my preferred choice moving forward. It's why the Prisma caught my eye. As for speakers, yes, we're open to upgrading them in time. Blade 2s are very, very pretty. 😏

We have however found that the mix is such that music significantly impairs the vocals.

I assume you mean that during movies the dialogue gets obscured?  If that’s the case then a center speaker could probably help.  If you’re looking at only a 3.0 system why are you looking at an 8-channel amplifier???  What specific speakers do you have, and does the Naim have a home theater bypass input?

We went a different way.  We replaced our rarely used 6.2 surround setup that used stereo bypass with a Sony HT A9 SW5 Dolby Atmos setup that's surprisingly good for music via Roon from the Nucleus.  We installed a KEF LS60 with a pair of KC62 subs in our living room.