A few months ago I set out on a similar quest. I even had similar equipment! Because I had 601 s3s for 20 years, I really liked the idea of a used set of 805s. It was like I had B&W blinders on. B&Ws are great, but it seems to be a truism that you might get a better speaker for your money if you throw your net wider.
One reason you might consider speakers first hasn’t been mentioned. Different speakers do better with different choices of amps and preamps. I upgraded my amp first and could have saved myself some hassle if I chose my speakers first.
I am stubborn as h€|| but once I threw off the blinders I ended up with used Vandersteen Quatros from a dealer I could trust. If you decide you are curious about Vandersteen, I have found their owner forum extremely helpful. Richard Vandersteen is also available to give advice which was a nice surprise.
The choice of Vandersteens informed my other system choices considerably, and I ended up with an Ayre amp and preamps - KX-R pre and VX-5 Twenty amp. Used Ayre equipment was reachable for my budget and Ayre, like Vandersteen, is super customer service oriented. Ayre takes in your equipment and will check everything and/or customize for a modest fee. I won’t pretend my path is for everyone, but it’s an example of how your path can change once you start considering other speakers.