ATC Scm 19 V1 Upgrade or what?

I would move up to the passive 40, a big improvement over the 19 (either version).

Yes, plenty of power, a great match.

The pro active 20 is roughly the same price as the passive 40. Since you already have ATC amplification, the 40 will give you more bass and plays louder. You don't have to deal with stands. Yes, going active with ATC will give you an improvement over passive but I'd still go with the passive 40s in your case.

Besides, the pro SCM20ASL is backordered at least a month, probably more; extremely high demand. You won't find it anywhere discounted below $6490 and good luck finding a used pair.

what are you trying to improve?  not specifying will just lead to nonsense replies

I agree with VV. I think your best bet is to go to the passive SCM 40 V2 with the ATC amp you already have. It will be just fine driving the bigger speaker.

My room is nearly 5x3 m .. I'm not sure if it's big enough for scm 40