French_Fries, it is my understanding that the group of products formed by M10, M12, M112, M302, and M301 up to serial 71, were all sweet sounding to the detriment of some emotionality at the micro and macro level.
the following generation of amps followed two diverging routes...
the higher end M312 stereo and later production M301 monos were much more emotional products than the previous 2 generations in the micro/macro domains, while the lower end products like M201 and M501 sounded somewhat matter-of-fact unless they were fed through the JRDG PC-1 rectifier. M301, M312, M201, and M501 are all withdrawn.
The current generation of amps is growing into a much broader family: M925, M825, M725, M625, M525, M125.
The early incarnation of the M625 stereo exhibited a denser harmonic content than M312 but in some cases sounded slightly less transparent. It is my understanding that the slight regression in transparency has been addressed by a minor internal change. The original M625 stereo in my system generated stage and images that were approximately 2/3 the size of M312... Driving the Vienna Muzik, it sometimes gave me impression of having to "work for living".... There was the slightest impression of the amp running out of steem on intense orchestral tutti.
M725 mono cleans up all the residual issues of M625... At least as transparent as M312, but with lots more harmonic content, equal or larger stage and images, authority galore, and oddly enough, greater control and musicality of the bass, in spite of it having lower damping factor than M312... Which points to the fact that published specs are not necessarily good predictors of product behavior. Oh yes, and apreciably better control of intermodulation in treble, which yields treble that is even sweeter than M312 without being dampened nor foreshortened. Bottomline: M725 replaced M312 as my reference because it is more resolving, more transparent, and more musical than M312.
M625 and M725 remain current products. The amp line is being augmented both upward and downward.... M925 monoblocks have been released in January and I have a pair on order. The M825 stereo will be released in April, together with a lower end M525 bridgeable amp, and an entry level M125 stereo. How will they sound? I do not know yet, and any conjectures on my part would be quite worthless.
Saluti, G.