RV, I don't know whether or not this will be helpful but I'm familiar with your listening issues, suffering from them to some extent myself. Historically speaking I've thought that 'depth of image' was the final measure of the quality of the stereo experience. For years I've focused on having the front of my speakers at least 6 ft from the wall. Got a nice 'airy' sound and pretty fair DOI. I accepted this and spent my time trying to get the right tonality. Very recently I got really experimental, for me at least, and decided to move my speakers back towards the wall. I've gone from 76" to 45". I've maintained my triangle, 10 ft apart and 11ft from chair. What I got was, for my purposes anyway, amazing. A much more focused, solid, mid-range and an overall more natural sound, not so airy and a bit of loss of DOI, but, and this was a real surprise, the tonality improved! Now when I play music the audio aspects no longer dominate my attention, the music does. FWIW.
BTW, Listening in mono might replicate your car experience but I doubt that you'd be happy in your room. Your preamp has a 'mono' option, you could try. Also, since your CJ also has two outputs, you could get a second pair of speakers and amp (small and cheap) and put them elsewhere in your room, somewhat close together and listen to them in mono. Much as I like frogman's comments about getting out of the sweet spot, perhaps doing so and having a mono option/second set of speakers would be the best. Lastly, FWIW, you've been listening to, and participating in I'm sure, music which is well understood and appreciated. When I listen to that music now on my system I try to avoid playing music which is less than involving lest I start listening to 'audio'. Most of my listening now is to music I'm less familiar with so I can listen to the music or the 'audio' depending on the music and/or recording, what ever. :-)