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

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. 

@grislybutter Speed Yellow has a little red in it. It glows in the sun. On the road on a sunny day you can see it a light year away.

No! The only Harbeth you are interested in is the P3ESR XD. The small enclosure is almost like having no enclosure at all. Most enclosures including the larger Harbeths are musical instruments, they make their own sound. The P3ESR XD is the closest you can come to a Quad Model 57 and maintain your sanity. Do not let it's size fool you. The limiting factor for most speakers is the tweeter and the P3 has as tough a tweeter as any speaker. It only problem is handling bass which it doesn't. Two subwoofers are mandatory for the best performance, not by adding bass but by taking it away from those little woofers letting them be what they really are which is midrange drivers. That can be done down the line. Two of the little KEF Balanced Force subs make an excellent match. 

Genius? My wife would argue with that.  

I'm still trying to figure out what all makes a speaker sound good to me. I can learn to like a lot of speakers, but I have found that when it comes to direct radiators I tend to like a 4" cone midrange, and 3/4" dome tweeter on a minimum baffle. Crossover up around 3500 Hz. Small bookshelves like this tend to have a great effect on me, often better than 2 ways with larger woofers, even though I can hear improved bass extension and lower distortion. Just add woofers/ subs to the little speaker and it's great! It's something about the dispersion characteristics of the smaller woofer and tweeter I suppose. 

For horns, I like full horn loading rather than hybrid designs, and smooth dispersion characteristics rather than full exponential loading like a Klipschorn of old. I think some degree of smooth off axis is taken into consideration on most modern horns now days.

In any case, I'm willing to try anything. If it works, it works. But if I were forced to buy without hearing I'd be looking for smooth on and off axis response with high efficiency and relatively easy impedance load. I'd be willing to sacrifice maybe some smoothness in response for better efficiency, so long as it's not too rough. I'm willing to sacrifice absolute impact / loudness for a smooth, natural and detailed sound. I don't like it really loud but I've experienced a sound I prefer more often with higher efficiency speakers.