the big one: how do you choose speakers? By what features, data?

OP,  …”size of speaker”.

Good question. I don’t know of any rule of thumb. My dealer has been to my house many times and we discussed extensively. But, while I can identify many speakers ridiculously large for the room they are in, and many insufficient… I don’t have a good enough knowledge to make up a rule. 

I choose them by ear only

@ghdprentice. +1

Simply spending money blindly without a plan for your bespoke system synergy is a recipe for big disappointment.

Audio - Rule of fifths

The truth is that for a high end 2 channel audio system we really start to see a jump in sound quality once we get past the $3500 price point. After this price point for an amp, DAC, streamer, speakers or whatever the quality starts to get into the higher end realm. After $3500 the higher you climb the price ladder the less improvements you will see.

It’s called diminishing returns.

We pay much more for only a 3-5% change in sound (notice I didn’t say improvement) when we go up the audio price ladder.

The matrix general philosophy here and going up is that you can enjoy 80% of the audio performance at a 20% of the additional price. The audio improvements vs added $$$ is not linear.

So how did I bridge the $$$$ outlay to my bespoke audio preferences matrix  in choosing speakers?

Simple ….

(1) Roll up your sleeves and go audition speaker options at your local dealer(s), and

(2);attend audio expos to source new model options in order to. Validate mag reviews

I am not  sure I understand what it has to do with choosing a speaker

Either I'm lucky or I just don't care enough anymore to shop for something as crucial as a pair of speakers, but that's mostly because I did my final major component shopping before I left L.A. for my current small-town home, which is a decent plane flight from any high-end store. 

Before my big move I spent a good many years as a hifi junkie in L.A. I developed my tastes. I made a nuisance of myself at many high-end stores. I went to many hifi shows.  In any event. I made sure I was satisfied with my rig before I sailed off across the high seas. As for my non-speaker components, when something breaks I'll get hold of one of the dealers I frequented when I lived in L.A.  Dealers whose ears I trust. And, yes, one of those dealers is Upscale Audio. Another is Gene Rubin.