any ATC experts here? Im considering SCM19's vs SCM20PSL Pro Mk2

SCM40s are the way to go if you can find a used pair at a decent price. In all respects, they’re a step up from the 19s and 20s in my opinion. I love mine.

ATC 20 passive, ATC 19A, ATC 40A, ATC 50A.  What do you want to know?

20 is quite lovely, not as dynamic as the actives, needs lots of stable current and Sound Anchor massed stands.  19A is introductory, beginnings of where active gets interesting showing what a modest active 2-way is capable of.  They are quite good.

40A could be for many an endgame transducer.  Sealed cabinet limits some dynamics and reach below benefitting from a decent sub.  Bass quite articulate.

50A now my reference.  Surprisingly significant step beyond the 40A in dynamics, bass response and midrange with upgrade to 'S' Spec tweeter.

Everyone is welcome to an opinion, but real world experience should trump those simply rendering one.  Preamp is the ATC SCA 2 which drives the actives hard.  Not everyone's cup of tea as there is little romance here.  Take no prisoners.

Every aspect tends towards live performance.  Not listening fatigue live, but very dynamic with headroom available to 112db with the 50A.

After several years of active transducers, most everything else seems a bit muddled, slow of attack and smeared.  If there is a deficit, it is in listening to poorly recorded/mastered material which is treated mercilessly and therefore unlistenable.

I've nothing to defend here with ATC, no ego in the game.  ATC's reputation long cemented before I came along.  Not the only game in town, but a very good one. Good hunting.  Cheers

@deep_333 plus one ...

I HEARD ATC ACTIVE 50 spkrs and was utterly blown away, so much so I questioned my system.  

I HEARD ATC ACTIVE 50 spkrs and was utterly blown away, so much so I questioned my system.