Looking for wider soundstage

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.

@backdoor , It is, but I have no idea what you will accept as reasonable performance. You might be perfectly happy with a system I would deem sub par. But you have spent a lot of money already so my guess is it is important to you. If it is imaging you want the first thing you have to provide your system is a symmetrical environment. Stereo is all about symmetry. If one channel differs from the other in any way the image is chipped away at depending on the severity of the infractions and in the situation I see in your picture they are legion. 

In a residential situation with the size rooms we normally have you want a flat front wall and two clean corners That extend for at least 6 feet in front of the speakers This should be on the short wall of the room. Both speakers see a corner and the listening position will be somewhere in the middle of the room away from the back wall. If you use the long wall the listening position will be up against the opposite long wall which will really create amplitude problems. With the type of speakers you have you will need sound absorption on the front wall, side walls and ceiling. The speakers need to see an exact mirror image environment. From there if you want SOTA performance it takes a little digital signal processing which scares the h-ll out of the analog crowd. Suites me. It keeps the price of digital processors down. 

I only mean to help and do not want to see you wasting money chasing a faulty situation that might be able to improve a little but still will never approach the performance it should, the performance you expect.