You might also consider age of tweeter fluid and capacitors. If these are old, the 6Ks might not sound their best, factor that in to any negotiations.

I recall @VirusKiller having great things to say about 18 bit versions of something, I don't recall which speakers. As always, let your ears decide.

Chris
Srces: Wiim Pro | OSMC Vero 4K+
Procs: HD621 > G61R > Minidsp DDRC-88D
Spkrs: 7200.2 + 5KC + 5Ks | iNuke6K > USC15 | iNuke3K > 2 x Crowson T108SS
Video: JVC HD950 & 1.9m React3 2.4:1 screen
Room: 5.8x2.8m | Various GIK Panels