+1 on what Nick says above.

Having owned the 6Ks, this advice is spot-on.

In my experience the 6Ks are easily the best of the speakers you mentioned, by quite some margin.

All these speakers are old now, so make sure you leave plenty of budget for getting them re-capped and new tweeters by someone who knows what they’re doing.

I’ve owned 6Ks twice, the first pair I let go, the second pair, which had re-cap and new tweeters frankly sounded and behaved completely different. Much more revealing, sweeter and subjectively tighter bass (likely new tweeters giving extra definition - better quality treble usually makes bass sound more detailed and textured).

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