Which amp matches best my JM Lab Mezzo Utopia ?

I would suggest that you need at least 100W with a transformer that can drive the bass woofer. I have a pair of JM Lab Alto Utopia and tried a few tube amps. Then I found that a hybrid amp is the best for these speakers.

I am happy with my Counterpoint NP100 platinum: 100W at 8ohm and 200W at 4ohm.

Aleko, I would like to respectfully suggest that you're definately over-thinking this whole thing about selecting an amplifier . . . and this is coming from somebody that very much likes to understand and think about the technical aspects of audio.

But the pile of opinions and discussions above, spanning almost three years . . . this is WAY more information than you'll ever need. Probably time to simply listen, think less, and don't second-guess your ears.

Vet93, from your experience I understand : 100W minimum.
Others have said it too .
The power of the amplifier appears to be the limitation factor in these speakers' case.

Kirkus, you are absolutely right.
Enough is enough !

Aleko, what amps have you tried on your Mezzo Utopias? Let me know what you think of them.....

Vet93, here it goes :

- Pass Aleph 3 - solid state single ended 30W.
The small 3 sounded fine with the Mezzo .
I would say it did the same as with 8 ohm speakers .
It used to get quite hot during operation.
There was the see through soundstage existing.
Output current is limited with the 3 though.
Subjectively this created the impression that the amplifier is trying too hard.
- Primare 928 monos - solid state, push-pull 100W.
At 100W a better match, maybe a very good match.
Good soundstage and bass line.
IMO these are very good amplifiers.
Easier operation but some clarity lost compared to the Aleph 3 .
- Gamut D200, solid state, push-pull 200W.
Good match especially that you can adjust the gain by the 4 switches inside.
Especially valuable for me as I use a tube phono pre-amplifier with cathode follower output and no line stage but only passive - selector and ladder volume attenuator.
Powerful sound, bass line was very robust, the speakers got in control .
The soundstage was very wide but not quite deep and see through like.
The highs were probably not that clear as with the Aleph but the mids were very good and the bass was much deeper .
The solid state character was still evident though.
The effect for me is that I get easily tired and want to try something else .
That is why I have started the discussion saying that I am going for a SET tube amplifier.
From what I understand it seems that the Marantz 2 you are using is a very good match for the Mezzo.