Historically, the first speakers to “wow” me were probably Martin-Logan Quest, followed by Tannoy D700. I’d like to hear the latter again sometime to see what experience says. I have heard the former subsequently in the same room (though last time I heard their new speakers with end fire array bass and ARC I thought they were very good!)…and chalked up my previous enthusiasm to youth and inexperience. After that KEF Q15 (first speaker I could afford that I liked), a DIY subwoofer from the Peerless XLS Application Note (830500 XLS12 +XLS12 PR in 35L), Quad 63 on Gradient dipole bass bins, Soundfield Audio Monitor 1, KEF 201/2, JBL LSR32 (would have bought these when current if they had grilles), Revel Salon2.
My most recent “wow” was JBL LSR705i when they first came out. Such natural tonality - with headroom! - out of a shoebox.
There have also been plenty of speakers that brought a wow factor, but in the sense of “wow what are they hearing in this; have they ever experienced live unamplified music?” Lowthers in back-horns, for example. Or Wilson WATT/Puppy, Avantgarde Trio.