This sounds a little too dramatic to just be attributable to changing amps. It sounds a lot like you have inverted polarity somewhere, which would do exactly what you’re describing to the imaging. I’d go back and check you have all your interconnects and cables properly connected positive to positive and negative to negative. If you do, I’d try reversing the polarity on the amp or speaker side (but not both) and see if things snap back into focus. The other thing to check is if your preamp has an inversion switch you may have inadvertently flipped in swapping equipment. In any event, this does not sound right.
One last thought. Not sure how it would cause this, but I'd go back to my prior interconnects if the new amp has single ended inputs just to take another variable out of the equation. Good luck.
One last thought. Not sure how it would cause this, but I'd go back to my prior interconnects if the new amp has single ended inputs just to take another variable out of the equation. Good luck.