I don't know if the following speakers are the "best" I've ever heard, but they fundamentally changed the way I thought about speakers. They were DIY units with a BMS 4590 dual concentric compression driver loaded in a 90x40 horn that was huge (I think over 20" wide) over a 15" woofer from Beyma. Active DSP crossovers (don't remember what, but this was the fin de siecle so we're talking fairly primitive stuff), probably expensive amps but who cares. Overpriced CD player (Burmeister, I think). I have no space in my brain for irrelevancies, so I don't know what brand the wires were. They combined the best I'd heard from really great conventional speakers (e.g. NHT 3.3, KEF Reference Model Four) with the dynamics one gets from real music.
I had always thought that horns were bad-sounding until then. I hadn't liked the few (Klipsch, C-V, DCM) that I had heard, at all. Those were the speakers that made me realize the value of controlled directivity and high efficiency.
Best commercial setup at any price from a hi-fi dealer: Tannoy D700's, driven b who cares what, it's the speakers and the room that determine the sound.
Best value for money speakers that I've heard: JBL LSR6332 midfield monitors.
Biggest surprise (positive): the imaging from KEF's little KHT3005SE eggs, that the plasma-ion tweeter in the Acapella Violon 2000 is not hype but pure glory.
Biggest surprises (negative): the bass from the Acapella Violon 2000 (because the rest of the speaker was sooo good), the way in which Wilson speakers consistently mangle music.
Speakers I haven't heard but would like to:
-Keele/Audio Artistry/PE CBT36,
-McIntosh XRT-2k (even though I don't generally like line arrays, I'd love to hear what can be done with 12 of the best 12" woofers in the world - Aura NS12-794-4a - 128 of the best 2" drivers in the world - Aura Whisper - and two lines of tweeters. And really, when you consider that they have over $6500 in woofers alone, the price isn't too unreasonable)