A deeper more holographic soundstage.

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 ....

OP, same quest here.  Was ok but things popped when I did what Millercarbon is suggesting. Symmetry in all dimensions to the inch, or quarter inch when possible.   Get a $39 Bosch laser measuring device.  I didn't get from your post what you've done to date so sorry if you've done this.  Unless or until you do this, its a fool's errand.  

Millercarbon is right about the EXACT angle necessary to position speakers.... That is mandatory...

Happy New Year....

Dchang05,  isn't this how you describe your new system?

I purchased BHK preamp, M1200, and P15 together three weeks ago. The first week they sounded flat and dull, but now they are phenomenal.

So are they phenomenal or did you lose soundstage width and depth?

Your old tube amps had pretty high output impedance which could cause frequency anomalies and depending on your speakers you could have shelving of the highs with the 1200s. Odds are if you equalized frequency response your perception of soundstage would be more consistent.  Perhaps a better statement is that your amp, pre, DAC shouldn't impact sound stage (as intended) if they are neutral.

The deep wide former sound stage may have been artificial.