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

The only measurements that I find of any value is the impedance the phase angle. A flat impedance curve with minimal phase shift makes for a very easy load, opening up all kind of opportunities with amplification (think single ended triods for example). A impedance curve that has lots of low drops and especially when combined with significant phase shift is much more difficult and requires an amp that can handle this (think old Krell or current Gryphon amps).

Then the sensitive comes into play. A very easy load with high sensitive (Zu Audio for example) makes it a perfect match to low power amps and as a matter of fact (and personal experience) might not work well with a high power amp (in my case, the volume control of the integrated amp was simply too sensitive to either it was too loud and one click lower and it wasn't loud enough). Low sensitive combined with a difficult load and you will need a monster of an amp with lots of power, but even more so lots of current.

@mijostyn

I am very impressed. I 100% agree with you, the P3ESR XD might just work its magic. You are a genius. (Now, about the 911, I question your color choice... but I will let it slide)

My favored brands, in addition to Harbeth, in the 2K used price range:

• KHL
• Buchardt
• Amphion
• Q
• Revival (no used, yet)

I wonder about Zu, may be too big for my small space.

I have to say: Harbeths are so ugly, they are almost pretty.

Hawthorne has a pair of Harbeth Compact 7ES3 for $2500

If you can find a pair to audition I recently listened to the Vienna Acoustic Haydn Grand monitors.  They were sitting next to a pair of $13,000 floor standers that I thought were actually playing when I entered the room...  Very dynamic and room filling with a good touch of warmth.  Retail can be below $2,000 I was told.

thanks @audiojan and @ja_kub_sz 

sensitivity, ​​​​​​placement, looks are high on my list. I am learning to read the impedance curve! :)

@drrsutliff the Vienna Acoustics are superb value. Not too many on the market here. I see a few in the US at any given time. 

@grislybutter If you’re gonna spend $2k on small bookshelf speakers, you may as well give the OGY a shot. I’m still amazed by them to this day. They just can’t outperform their size and have bass as deep as full range towers (like the KEF LS60). But the magic is truly there. And it sounds even better when you upgrade amps. I went from a Tripath chip amp, to a cheap vintage Continental Edison A/B amp to a Creek Audio 4240. It just keeps getting better.