Speaking as an ATC fan and ex owner of 100A's some time back before I got married and needed to sell them (the things we do for love eh?), I was mightily impressed by the 4367's driven by a stack of modern Levinson gear probably costing way way more then the boxes themselves. I have to say I loved them for the 'ease' they gave the music although on a much loved Buddy Holly track (Everyday), it could be argued his voice was perhaps a little larger than life (smaller UK room syndrome again?). I haven't heard 150's lately but hearing the current spec ATC 100A's brought tears of recognition and admiration to my eyes (I used to regularly visit the factory with prospective domestic clients and all but never lost the sale, so worth it to everyone and this good vibe about the brand has lasted decades now). These days, the high end market is heard with the eyes over here mostly, so no matter how 'good' the 4367 may be, it's judged as too cumbersome and retro-niche to sell sadly, by the few remaining higher end dealers here
In the domestic arena, we just don't get the chance to hear many truly world class professional speakers, as it seems that companies like PMC, Dynaudio and Focal do specific individual ranges and never the twain shall meet (ATC and Harbeth seem to do wood veneer or painted versions of much the same thing for some of their shared-market models), Harman never pushed JBL here really and Tannoy had some rather meocre domestic lines and again, the larger pro models rarely if ever came our way to try. Fascinating to read here of Genelecs, which I've read and heard so much about and wish to hear properly, as well as the larger Neumann's which look just right in higher end monitor prices (half that of an equivalent active ATC I think).
P.S. This may only be relevant to the UK or maybe European market, but my understanding of a 'powered' speaker is basically a speaker with passive crossovers but with a built in or bolted on amp pack. An 'Active' speaker to 'us' is one where the crossover is done electronically *before* the amps, these amps then looking directly at the drive units with nothing in between. Is this the same for the rest of you all?