I was never a fan of LS3/5a's and Kans as they have no real bass (only a one note thump in the case of ALL 3/5a's and I've sold all varients at some time or another)
The best years for Linn speakers using KEF drivers was '83 to late '84. I had Kans for a short while (sounded hopelessly thin at home although the same pair sounded wonderful in my mate's system and longer room) and Isobariks back then. The Kan had a tilted 10db but linear response rise from 100 - 1KHz and placing them tight to the wall helped to flatten this, along with the bloated, fruity 'Sondek (or dull Rega cartridges) we all used at the time.
As stated earlier, KEF b*ggered up the drive units and all speakers using the B110 suffered catastrophically from this. The 3/5a was ruined forever and the Kans and Isobariks went all screechy and "hard"- just in time for Linn enthusiasts wanting to investigate CD reproduction - they ran a mile LOL!
The "upgrade" to the higher power B110 flattened the response of Kans and Iso's but the magic (and the LP12 era) had passed and they were never the same again.
Tukans are far superior IMO, especially with the later tweeters with the ribs on the front rather than the meshes.
I think it fair to say that in my experience ALL Linn speakers made after that awful Nexus thingy need to be active to sound anywhere near competitive. Activ Tukans can be really captivating, especially if everything's bought used to reduce costs..