Klipschorn Imaging

Khons will image just great if properly set up. I have had them 21’ apart and they imaged fine.
Your set up will not affect the imaging only affect the bass because their not booth tight into corners
Most of your imaging takes place in the upper frequencies their are some things I would like you to check.

1st is your source a good 2 channel stereo source

2cnd is the polarity from amp to both speakers correct

3rd put you ear to each tweeter make sure they are working

4rth compare each speaker and see if all the drivers are the same polarity and terminals match at the barrier strip.

5th Is it time for new crossovers?

Being that you are using a tube amp the imaging should be vivid and holographic Because Khorns are in corners does not affect their imaging but it does affect their depth of sound stage. When I had mine set up you could picture the orchestra instruments and singers in their prospective places.

" 2cnd is the polarity from amp to both speakers correct

3rd put you ear to each tweeter make sure they are working

4rth compare each speaker and see if all the drivers are the same polarity and terminals match at the barrier strip. "

How do I find out if the polarity is right from amp and how do I check if all drivers are same polarity?
How do I know if it is time for new crossovers?
I am sounding very newbie probably because I have a lot to learn- do enlighten me.

Have you tried the Onkyo by itself instead of using it as a preamp? There is always the possibility you have a bad match between the Onkyo and your amp.

The Onkyo has a high noise floor and sounds brittle, harsh, like a bad solid state from 1980s. It works out well with much less sensitive speakers. The pre- amp section is also not the greatest-not super quite & I suspect the DAC is not the best. I don't have any other significantly better DAC to compare it to. Most of my sources have HDMI out. There is no stereo preamp with HDMI in.

Honestly, you sound like you are where I was in the late 80's. If you are a serious audiophile, I suggest you develop a comprehensive plan. Start by auditioning any and all the components you might consider. 3D imaging require all components functioning as one. This is what audiophiles strive for, and it does not come easy.