Looking for wider soundstage

@backdoor , I had a look at your pictures and I hate to bring you bad news but even with digital signal processing you are never going to get a decent image with your system as it is set up. It breaks almost every tenant you can imagine. It is fine for everyone's background music pleasure but that is about it. Your system needs a home that is more in keeping with it's intent. No amount of room treatment and expense is going to change this. Your next mission is to find a more appropriate home for it either in your house or eventually another if it is that important to you. 

dekay I’ll give that a shot. 
 

mijostyn that is bad news. 

mamba like spatial audio for example?

A sure way to increase your soundstage in an untreated room is to hang a soft blanket or even a sheet on the wall behind your speakers. Give this a try. If you hear a difference (you will) you can try the side walls at around the 90 deg angle between your seating position and speakers. 
 

hopefully you have a dedicated space and can do this. 
Give it a try and would like to hear back on your experience. 

If you have planar ribbon tweeter your going have a reduced sound stage domes they are just wider dispersion.  As for as capacitor go Solen are bottom of the poly barrel. If you have a tube preamp you will have a wider sound stage. My system is all FETs and MOSFETs and provides a sound little more tube like as related to sound stage. Caps like TRT, Dyna Cap, and other metal foil polypropylene have a much improved dielectric absorption but expensive.

I have this Golden Ear Center speaker it’s very clear but 30 degrees it’s output is very low. So borrow some speaker with out Ribbons and see if that does not help your imagining.