A deeper more holographic soundstage.

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...

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

I already speak about resonators in acoustic controls.... But instead paying big money i bought copper lure for fishing line among others things for few cent and try different size of other copper little bells with success...

Other active device controls would do marvel also at peanuts costs...

 I use it to ionize my air room and the effect is astounding, on par at least with my active Schumann generators grid (10 bucks by pieces)


Sometimes i think that placebo effect work by pricing the object costly and waiting for selling it...It is way evident with costly acoustical materials...If somewthing work it is NOT because his brand name is costly sometimes....i never bought specialized acoustic materials but chose by listening experiments with completely cheap one and my room is like a costly hall soundwise....


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Source can make a big difference: I was comparing two CD players. Same CD in each. same interconnects with both players played simultaneously- switching line inputs from the remote meant A/B blind testing was easy.

The main difference between the two was the 3D soundstage. One (a nearly top of the range Naim) had a wide but flat soundstage . The other (Vitus) went back way behind the speakers in an incredibly deep way. So please do not discount source.

When I replaced my BAT VK5i and 150 SE monoblocks to the new setup, my sound stage shrunk big time. BAT is known for big and deep sound stage, but I didn’t expect I would lose over 50% of the depth and 1/4 of width. So the equipment is important. I changed PC, IC, and speaker cables. They made less than 5% difference. 
I moved the speakers further away from the back wall and pointed them outward and that helped. But you can only do so much before the soundstage losing it’s focus. So I agree equipment may be the most important factor.
 

Source can make a big difference: I was comparing two CD players.

For sure source is important...

But between all dac or cd players, half of them will sound wrong and the other half relatively good (it is a way of speaking i dont know the exact number).

It is the same thing for speakers and amplifiers.... It is very important to chose our basic element in the good half section of possible relatively good component....

BUT when this choice is done, the main reason for the lack of information in S.Q term are the uncontrolled mechanical vibrations and also the electrical noise floor which is too high all along the house and mainly because of the room and bad acoustic cause a bad timing of the sound wave reflection and mingling and reverberation and echoing...

These reason are the main problem if the components are well chosen to begins with and are on the right section of the audio products offered in the market...

In a word source count, but embeddings controls count on par with it ....