Which components knocked you out on first listen?

Passive preamp!

Totally blown away when I first tried a passive pre. It was the reference line preeminence 1b. My jaw dropped.

That and when I started making my own thick solid core cables and interconnects.

System-wise - dCS P8i ~ Focus Audio Master 2 ~ Vitus Amps;

Individual Component-wise - Focus Audio FS-888, Magico Model 6, PrimaLuna Prologue 2, Yamamoto HA-02, Zu Definition Pro's, Rogue Audio M150's, Aurum Cantus V3M, REL R505, Pathos ClassicOne

the best system that knocked my socks off was back in 1979-80,I was 19-20 y/o I walked into Northridge audio,northridge ca,and heard for the first time- accustat model 3 with accustat tnt amp/preamp comb.and the kenwood kd5500 (marble base table )I think it had a dynavector cart .From that point on I was hooked ,since then my wife calls be a geekphile instead of a audiophile,lol.My system now is all Mac intosh /w maggies 3.6 ..love it!!!!!!!!!!! harry T

Avantegarde Duo driven by Audiopax Model 88s. I too have been an audiophile since the mid 70's. I have been a fan of Rogers, ESS AMT 1B's, Magnapans, Dalquist, Acoustats, KEFs, Infinity Composition Preludes, Usher AC-10s, ....but they all sounded like stereo. Being the only thing I like better than listening to stereo is listening to live music. The Avantgarde Duos were the first speaker that completely caught me off guard (because I HATED horns) and changed my perception of what a dynamic loudspeaker should sound like...live music. They truly have the ability to touch you on an emotional level. I have, no kidding, seen grown men weep...

Lavardin amplification, Avantgarde loudspeakers, and to a lesser extent Totem Model Ones.