I replaced a solid state Marchand XM44-3way with a Marchand XM126-3way. The improvement is not subtle. There is just much more layers and depth from the same recordings. It's a classic case of not knowing what you are missing until you hear the difference. The sound stage at least doubled in depth giving me more clue to the location of instruments relative to the voice. The real big difference is in the tones. Can you say PHAT? The notes are layered with harmonics that I had not heard before. Every note is more robust and layered. Mid range is thick and juicy making the female voice sexy and sultry. The highs effortlessly soars and trills with just the right decay that lingers to put a smile on your face. Bass is more solid giving the music a good foundation to build on. The music is just so succulent you want to bite it. I just can't quite describe the improvement in words. Let me give you a visual metaphor.
With the XM44 I was listening to Twiggy.

With XM126, I am listening to Jane Mansfield. aa

Need I say anymore?