A deeper more holographic soundstage.

From what I can tell in my limited time here @baylinor, it is a serious uphill struggle.  Unfortunately it is easier to change a fuse or cable and claim a big improvement than to actually take the time, learn, learn some new skills, break dogma, and have a real, substantial, and long lasting improvement.  Once you solve those acoustics issues, then you get even more enjoyment from that upgraded hardware. If you don't address acoustics, then you top out early in performance. Some audiophiles keep "tweaking" in hopes of moving forward. Others just give up. 

From that I concluded that sometimes electronics do matter for sound stage even in the solid state category.

Electronic design quality always matter but most of the times way less than good controls of mechanical, electrical and acoustical dimension....

Wow. Reading all the comments really demonstrates there's a long way to go in audio before we all agree. It almost seems totally subjective and opinion driven sometimes. 

Some here overlook all recordings have reverb to some extent. You can listen to one speaker with a mono recording and still hear reverb.

Depth is nothing more than reverb done well. Done poorly and it's unconvincing that it's music being performed in room or venue. Live music performed in a church has depth. A piano in a room has depth. How BIG is the church and how big is the room?  Once you can sense that, you know your can be happy about your system's ability to reproduce depth. 

The answer to the OP: Phase. Do phase well (especially out of phase information) and you get "depth."  

A piano in a room has depth. How BIG is the church and how big is the room? Once you can sense that, you know your can be happy about your system’s ability to reproduce depth.

The answer to the OP: Phase. Do phase well (especially out of phase information) and you get "depth."

Very good remarks...

I concluded that my acoustic treatment and control were right when i was able to hear this difference between the relative size of different recording live location, being it a small room or a church, i will add with the same perfect imaging in the 2 case...

Doing phase right for me was by listening experiments installing different acoustic devices or surfaces to make the waves timing with one another.... That ask for some balance between reflective, absorbing and diffusive surface....But also using resonators of different size....

Room treatment...you can use acoustic foam at all the early reflection points.  That means ceiling and floor too if possible. Use the mirror trick. This the cheapest and most effective. However WAF is zero.

Super tweeters don't work for this purpose. I have a pair of Townshend's lying in the cupboard.

Biggest jump up I had in creating a large soundstage was HFT's from Synergistic Research.  

Tunable resonaters are good, especially in combination with HFT's.  Need minimum two, more is better.

Synergistic Research make a very good one, I've forgotten what they call it, but it  has settings for many different ambiances and according to Jonathan Valin, it really works. Expensive though, around 3K...