For the 3rd time, my question is about how to read the reviews. Can I do an apples-to-apples comparison of a SMSL DO100 and a Aurilec Vega? Or are these completely in different classes for different purposes? And if it is the latter, how do I separate the reviews?
I believe with those 2 you can, the main reason you wouldn't be able to is features, i.e. DAC a only has USB in whilst DAC B uses Optical and Coax. As long as both dacs can be used (ie your source has outputs that the dac can use as inputs) then you can compare, there are things called DDCs which let you convert one signal type to another but that is added cost.
Something you should consider is making sure to look at both subjective and objective reviews. R2R and NOS dacs don't mwasure as well as Delta sigma dacs, but are prefered by some. Similar to how some prefer tube amps over solid state amps. Amir's SNR chart should not be treated as a ranking of the sound quality of the DAC. Amir also has a great post about to read his measurements.
As for 8K, your scepticism about "no difference" claims is warranted,
https://www.techhive.com/article/578376/8k-vs-4k-tvs-most-consumers-cannot-tell-the-difference.html a double blind study shows however to most people at reasonable viewing distances there is no difference. Our eyes have a maximum amount of detail we can perceive, this is why apple brands all it's screens as retina instead of slapping 4k or 8k on it. If you want to know if 8k will make a difference go to an optometrist and get your vision tested, you can then use that information combined with seating distance and screen size to work out if you could benefit from 8k.
Going for a seperate amp is 100% the right call, if there's a new standard, or codec released you don't want to have to buy a new amp every time or if something breaks maybe it's the amp maybe its the dac, but if it's all in one box you can't just replace what broke you have to replace the who box.
I'd recommend getting the miniDSP OpenDRC-DI it's $325 for 2 channels of room correction, it has optical/coax in and out. You will need to get a measurement mic (You can hire expensive ones or you can buy calibrated ones on amazon for pretty cheap too) and to take some time taking measurements and there's bith free and oayed software that'll generate filters for you to put into your OpenDRC. This is more work than Dirac Live but the advantage is like with seperate amp you don't have to buy it over and over again (you will need to remeasure if you change anything in your setup, especially speaker placement) but it will blow you away how much better it sounds. Room corrected/calibrated cheap speakers can sound better than high end uncorrected speakers. Even with room treatment, being able to perfectly time align speakers will really improve imaging
On your budget I'd recommend looking at the holo spring 3, the preamp module is amazing and very similar to the serene for only an extra $500 you won't find a better preamp at anywhere close to that price point
PS one last thing about resolution. There are many things that affect video quality, mainly bitrate. As someone mentioned there 1080p tv being an improvement over 720p even though that chart suggests it shouldn't. Streamed video be it from netflix youtube or a live tv broadcast is always compressed. Hugher resolutions have hugher bitrates (ie less losses due to compression) this is why watching 4k youtube even if your screen isn't 4k looks better. You should also consider that a more expensive 4k tv will look better than a cheap one bc of things like dynamic range contrast. That chart is only about what is a perceivable resolution at a guven distance for someone with 20/20 vision. Not if content at those resolutions are discernable
