$3500 floor standing speakers used. What would be your choice ?

Well, after 25 years I might want to upgrade even if I still like the speakers.

Rooms will be changing, that's not part of the equation here, they should sound good in any but very small or very big room.

mulveling,

I see. I agree, coherence is very important, single driver speaker without flaws is an almost unachievable goal.

Yes, choosing Tannoy would be a very complicated matter, especially if you can't audition them. I also understand that the better ones will go over $5k used .

@inna 

Given the limited amount of power you have on tap, would a good pair of bookshelf speakers paired with powered subwoofers make sense in your environment?

That would make things more complicated and probably more expensive. Integrating subwoofers can be a challenge. I like coherence. But theoretically yes, I have enough room for that.

60 good tube watts is not little at all for a medium size room. The amp sounds quite powerful with the current speakers.