Unless I’ve missed something scanning through the thread, OP you haven’t mentioned the keyword which would be the key to “needing” an 818v3 over an 861v8 - MQA.

What are your feelings on this format? Is it enough of a deal-breaker for you that you really need MQA and therefore an 818v3 (or 218), etc., instead of a full surround setup? If not, the 861v8 will likely sound near identical with other material feeding 8KSE.

Secondly, I realise you feel at the moment that your priority would be 2-ch performance, but let me ask you, have you heard a Meridian 5.1/7.1 surround system properly setup (e.g., with MRC - Meridian Room Correction - done well, etc., full bass management...) for exceptional music reproduction? I ask because there is a misconception (due to most of the surround sound market being focused on cinema) that it is inferior for serious music listening. However, Meridian surround systems were never designed with solely cinema in mind - in fact, back in the day, Meridian were pioneers of hi-res (DVD-A) and thereby hi-res multichannel audio. So don’t assume that 2-channel will necessarily provide better performance/enjoyment in a Meridian ecosystem. E.g., I believe Richard Hollinshead once commented that the 861v8 was identical to the 818v2 bar the extra channels and processing - if one removed those, the noise floor would be the same.

FWIW, I started firmly in the 2-ch camp and went through various Meridian setups (all miles better than fairly esoteric analogue setups I’d had previously, e.g., Naim, etc.) culminating in DSP7200.2/818v3 which really are sublime. Then out of curiosity I listened to a Meridian surround setup done right. Now I have a legacy surround system (as in my signature) and couldn’t be happier. True multichannel recordings are insanely good (if you can get hold of a few of the Everest 3-channel recordings, they are worth taking to any demo) and Trifield and the other proprietary processing turns my 2-channel recordings into multichannel with stunning results. My wife loves it too - it works utterly seamlessly between music, movies and TV and sounds amazing on all of them. We’re no longer tied to a narrow stereo ‘sweet spot’ where only one of us hears things as they should, as the centre anchors movies and Trifield anchors music. We no longer have to set the speakers absolutely ideally and live around the system quite so much as MRC and bass management (well placed sub) takes care of the worst room modes.

So far (and I hope I’m not tempting fate!) Meridian gear has been the most reliable Hi-Fi gear I’ve owned and I’ve not had a failure yet. Considering I’ve regularly bought older gear, 20+ years old, I personally don’t have much of a concern in this regard. DSPs and 861/818 all have linear power supplies and seem to be pretty solid.

Lastly, even if Meridian continued to just churn out the same old Stuart/Hollinshead designs for another decade, they’d still sound better and (especially in the case of DSPs) be years ahead of most designs out there. In this respect, Meridian are perhaps a tad victims of their own pioneering? What I mean is, they were doing active and DSP 30-40 years since, only in the last 5 or so has this notion started to enter the mainstream. But they have had decades to really understand all the design parameters which really matter and only a few years since they were so far ahead the others are still largely playing catch up.

In other words, if you love the sound, don’t sweat that stuff. Tech always marches on, but it doesn’t mean the latest and greatest in terms of features actually performs any better. Having listened to a lot of gear, I still reckon the 861 is the best *sounding* 7.2 channels out there - is sound quality or the latest gimmick higher on your priority list?

A final thought - for a few years I ran 2x DSP6000 (predecessor to 8Ks) either side of a large TV for music and movies. They sounded awesome. But this didn’t work when we moved to a projector with a nice big screen as it meant compromising the sound by having to push the stereo speakers further out towards the corners of the room than was ideal for best sound reproduction. I don’t know your room layout, so you might get away with 8Ks at your chosen screen size if you go the 2-ch route, but I think it’s something to be aware of and make sure to plan the whole thing out with care if you go this way. With 2-ch you won’t have the same ability to compensate for speaker layout to accommodate a large screen as you would with a processor and multiple DSPs, and you don’t want to go for too small a screen to make that work. If you end up with compromised speaker positioning for 2-ch ‘purist’ setup, you run the risk of it sounding no better, or potentially worse, than a well-implemented surround system.