Solving the "complex music problem"?

That's more clear @frogman , thank you. I think that is a common outcome in setups. People say what they did, then claim to have way better imaging but what they did can't do anything but the opposite.

Hi, this is the OP,

So many helpful and interesting comments here. I can't reply to everyone, but I can thank everyone. What a great community. You've definitely given me a lot to think about.

To the many people here (and elsewhere) you've given me pointers on positioning my speakers, thanks. I've moved them further from the wall, helped immediately, and I thought I was being careful about that. I've also been playing around with how much to turn them in towards the center. 

Thanks to everyone who said they've noticed the same thing and that at audio stores they always play simple music to make the rig sound best. IMHO if the music is simple enough, with a little reverb, even vary entry level systems sound terrific. It's when the music gets more complex that the better systems make the most difference.  It's always been surprising to me that there wasn't much talk about this. Nice to know I'm not imagining it. I now think that a lot of the reason people don't talk about it is that they normally place music from smaller ensembles, so it isn't that big of an issue for them.

dcoffee makes a good argument for why my theory of why the problem occurs may be wrong. I'm 3/4 convinced, but still not sure. As a Bayesian would say, you've caused me to significantly rethink my prior assumptions. 
jeffseight, on the other hand agrees with my original thinking and puts it very well. "If you consider that in symphonic music live you hear each instrument  however in a two channel stereo you hear only on instrument ,the driver, it seem obvious that the two can not compete." If any readers, say, design stereos for a living and definitively know the answer to this, I'd be very curios to hear it. 

Varidian notes that live music has this issue also. You're right. My rethinking was greatly influenced by the fantastic concert I attended last night in Ann Arbors' "acoustically perfect" Hill Aud with an excellent sound system. It was a music festival with a bunch of different groups, so I got to hear a lot of different styles. The sound was amazing. But when I listened and thought about this particular issue, I realized that the sound was "mushing all together" there, almost as much as it does at home. So, to a significant extent, that's just what happens when a whole lot of sonic vibrations share the same air. This insight has helped me lower my expectations in this regard, which helps. 

Many people say the biggest issue is the source. Totally agree. I was streaming HD music from Amazon and the complex music problem was a big issue. Then I switched to Qobuz and the improvement was immense. IMHO the single biggest difference maker in audio is the quality of the recording itself. That said, even with great recordings I've still noticed that complex music presents problems. 

Thanks again for all your thoughts!

What's the difference between the "illusion of pinpoint imaging" and actual pinpoint imaging? Isn't all playback on any device an illusion? Are there tiny musicians trapped in some amplifiers? These are important questions...or the illusion of important questions.

What's the difference between the "illusion of pinpoint imaging" and actual pinpoint imaging?

No difference, perception is reality.

Big difference.

You are listening to a great orchestral performance recorded in a great hall on a well balanced system. Think London Symphony in Kingsway Hall recorded by Kenneth Wilkinson for Decca. There is a passage in the score for solo piccolo. One hears within the soundstage a perfectly placed image of the piccolo with natural timbre and no placement waver. One can literally point to the image of the piccolo within the soundstage and say “There it is!”. Even as the piccolo ascends into its highest register natural tone is preserved with no high frequency splash making the piccolo sound the size of a tuba. Beautiful! “Actual” pin point imaging.

Then there is another passage where the piccolo is playing a unison passage with clarinets and xylophone creating a unique, even odd textural blend. The piccolo sounds as it should, blended and as part of the instrumental “mix”. Much harder to isolate it within the soundstage. Play this recording back on a system with speakers  (or, whatever) which have an accentuation (distortion) at say 2000-3000 Hertz. If the piccolo is playing in that range (not uncommon) the sound of that instrumental mix will lose the sense of blend and the sound of the piccolo will be accentuated as well. It becomes more isolated within the soundstage. “Illusion” of pin point imaging.

“Perception?”, yes. “Reality?”, no way.