FWIW, I had a heck of a job a few years back deciding between 7200.2 and 5200SE. It was a close call as they both offered something different. After several extended demos, my opinion was that 5200SE were very good, and had a lovely refinement at the top-end. 7200.2 were all round great - bigger, more effortless presentation, cleaner, more extended bass, etc. I think this is simply down to the physical construction, size and power of the bigger speaker. E.g., dedicated midrange amp/DAC/driver (and TPX, not polypropylene), Meridium construction for a much more inert cabinet, psychoacoustically a bit more life-size, double the watts per driver/channel... in the end I went with 7200.2 and spent a few happy years content with my choice. I think I could have doubled those differences if I had been choosing between 8Ks instead of 7200s.

They replaced 5200.2, followed by 6Ks, in the same small room. I'll say I got all of those speakers working really well in that room, sound-quality wise, but the 6Ks looked a little big physically for that room and you did feel you were sitting "under" them. But owning both 5200SE and 8KSE you're already well aware of physical size differences.

Still curious as to whether you are comparing 8K to 5200SE/HC, the latter in a Trifield/surround setup? That is quite a different comparison, as Trifield (and perhaps later, a Sub hidden away) makes for a different presentation, which muddies the waters again. Looking at your signature, I see you have a 7200.2 HC and 861v8, so assume you are familiar with this difference also... Is this for your UAE rig or the home one?

Do you know the service history of the 8Ks...?

HC: 861v4/ID40/LPS, DSP5000, DSP5000VC, DSP3100, SW1600, HD621, Oppo BDP-105, Sony VPL-HW55ES
2-Channel: Oppo BDP-105, TEAC VRDS-7/Trichord Clock 3/PSU, 551, Quad 303, Harbeth Compact 7ES-3, Kimber cables, Russ Andrews mains and supports.
Previous Meridian: 5000C, 5200SL, 7200.2, 6000, 562V.2, 568.2mm, 800v4, 808.2i, 818v2/v3, 861v8, 502