The Levinson Sound?

Owned ML-2, No 27.5, 23.5, 20.6, 333, 336, 33H.  20.6 were the best sounding.  Preamp wise ML-6B, 7A and 32 Reference are the best

I also ran a pair of stacked Quads for over a decade with a pair of ML2s so I am qualified to comment.  Yes the ML2s can and do sound wonderful with the Quads but do sound dark and grainy when compared to some of the better modern amps.  

That said, I no longer own any ML amp (I prefer Goldmund amps), though I still own and enjoy a ML-7A preamp, which remains one of the best preamps ever

Having owned 3 pairs of ML-2s, I can say with confidence that they are NOT the best sounding Mark Levinson amps.  They do have somewhat "dark" sound that plagued some of the early ML amps, and they can be hard (and $$$) to repair if and when they fail, and they DID fail.  

27.5, 23.5, 20.5(6), and later 3XX series amps are all much better sounding