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

Asking for advice on which speakers to buy or listen to is useless.  Even good speakers vary a lot in their plusses and minuses. First you need to know yourself, what factors you must have and which make a speaker impossible to live with. Then you have a chance to pick speakers. But you must listen yourself after you analyze yourself. The only thing you can hope from others is not what are great speakers but their analysis of the sound of speakers they like(and you have to hope their analysis is accurate).

The Sonus Faber Sonetto V's are a bit more dynamic on the top end than the older Sonus speakers and could be just what you are looking for. Even better if you could afford Olympicas or Serafinos. You should however hear them first.

I had the Bolero's many years ago... good speakers!   I also like the Proac and Tannoy suggestions.  Just make sure you get speakers efficient enough to pair with 60 WPC tube amp.

Just saw some Tannoy on TMR today.  Real close to your original 3500. Nice cabinet

Open baffles open and relaxed if you have room.  Won't be a problem driving them.

Many speakers take too much power.  

+1 for Totem.   Tremendous value and all around excellent speakers.   Super easy to drive.   Might look at the Bison Towers or similar.