Here's a pic of my listening room:
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It's a dedicated room so I could do what I like. I like the sound. Mine's an extreme example but I got there over a few years. In particular I did not like side wall reflections hence the panels each side of the speakers. Some people like side wall reflections. I sit upright in a that chair but with my feet up. I also sit in the semi darkness.
My set up is with a single sweetspot. It's a bit more difficult for two or three listening positions but that seems to be why people use the MMM (moving mic measurement) system, or Diracs multi position one.
Going back to your first post, I responded by saying that bass is your first target to correct, the 30-300Hz range. To do this I used solely measurements using frequency response (with 'no smoothing'), waterfalls and spectograms, and finally the Real Traps Test Tone CD of bass frequencies and my ears. You may be able to get this better using only DSP/EQ, or only subs, but when using bass traps you also get the decay times down. I understand DSP/EQ does this too to some extent but I don't know from experience. What I do believe is that lowering decay times is a big factor in the improvements to my sound, especially bass.
The higher frequencies are harder to understand from measurements because they will include not only the direct sound from the speakers but all the various reflections arriving at different times. In this area microphones do not behave like our ears and brain and simply sum these things up. Our brain acts differently (called psychoacoustics - see for example the precedence or Haas effect, equal loudness or Fletcher-Munson curves). My approach was to remove reflections, using absorbent panels, and then look at the frequency response and making broad EQ adjustments to this, like tone controls. The aim was approximately flat but in truth I used mostly my ears to get it to sound good to me. I struggled at first to get good detail in the percussion but eventually managed it.
Looking at your photo in your first post, the position of the speakers and the way you listen (judging by your leg position) won't help with what you hear.
Symmetry is an important requirement, each speaker ideally being equally distant from the side and back walls and better still in a symmetrical room. Your right one is very close to the corner, your left is not. This will affect bass and higher frequencies. Indeed if you imagine a ray of light coming from your right speaker (which is how the frequencies over about 300Hz typically behave), reflecting off the side wall like from a mirror and then to your ears and compare that with how a similar ray would arrive at your ear from the left speaker you might guess, rightly, that the left one has longer to travel and would arrive later. That would mess up the sound.
Placing speakers in their ideal position may be domestically difficult but you might consider placing them for listening then storing them in the corner when not in use. Same applies for your listening position. An alternative would be to put some absorbent material right beside the right speaker and assume that the left speakers sound doesn't reflect at all. If that doesn't help then an arrangement like mine with panels by both speakers should do it.
If you noticed the difference a coffee table makes then putting a rug on the floor would be a good idea (some say we don't notice floor reflections because we are used to them). Definitely worth experimenting.
On ceiling reflections I'm not convinced. My speakers have a narrow vertical dispersion pattern and don't have any ceiling reflections that I can hear. I did experiment by jamming some insulation (you could try a duvet) on the ceiling with a 'T' shaped piece of wood. Perhaps ask your speaker makers if it might be an issue. Of course how close you sit to the speakers has an impact on this.
'The Thirds' positioning that I gave in my linked post is designed to reduce the impact of bass issues but also reflections. Again worth an experiment even if it's not practical for you long term.
To sum up, symmetry of room and positioning and removing reflections (as well as controlling the bass) means I hear practically only the sound direct from the speakers. My brain then sums this up to create a phantom image somewhere between the two speakers. After that it's the recording that dictates how the sound is spread. Usually I get rock solid central vocals, instruments spread around in the space, sometimes with a bit of depth. I also hear a lot of detail, such as percussion or subtle harmony singing. I do not get imaging wider then the speakers. A sort of good headphone experience but in the space of the room.
