Biggest impact on you?

From what I have, or do, own.
Audio Research tube amps and preamps.(some other brands are good too, but this was my first exposure to REAL GOOD SOUNDING tube gear. not just so-so stuff like reworked ST70s :)
Soundlab Speakers. - can't say enough - unsurpassed, imo.
had to have them after hearing just one note)

Other outstanding products would buy but didn't.
Digital front end from DCS. Ive owned most of the bid name brands - Krell, Theta, Wadia, but DCS sent thing to a new level, imo.

Largest system from Meridian back in the late 1990s (would need to look up the name)- made the hair stand up on the back of my neck and arms.

Running Bitperfect on iTunes to my Centrance DACmini to my stereo was a tremendous improvement. Granted, its the poor man's path to computer audio but it opened my eyes (ears) to what awaits.

Three components come to mind that had a huge impact not just for their
sound, but also for the education that they gave me about system building:

I will never forget the first time I heard the AR SP-9 in my system. It was
the first time that I had bought a brand new component and paid full price;
this made the disappointment all the more intense. I also will never forget
the fabulous sound that it had made in one of Sound by Singer's room in
a system consisting of Snell Type A IIIi's, VTL, Roksan/Koetsu, MIT. I
thought there had to be something wrong with my sample, as it made my
system sound bleached and dry. I took it back to Andy's, and listened to it
again in their system: glorious sound. This experience taught me the
importance of component matching, and the fact that some components
really are more transparent than others. The components in my system at
the time where not up to the AR's transparency. It was an invaluable
lesson.

Around the same time ('80's) I heard the Stax F-81's in a friend system. I
fell in love with their midrange and decided I had to have a pair. After a
couple of years of searching I found a pair. Brought them home thinking
that my "very powerful" Moscode 600 would not have a
problem driving this notoriously difficult speaker. It "drove"
them OK, but the sound was grainy and slow. Tried different cables,
preamps (AR SP-9 was one of them), to no avail. After months of trying to
get them to sound like music, I realized that it had not occurred to me to
try the Dynaco ST-70 that I had sitting in a closet. I figured what the heck.
I could not believe my ears. The lowly 35 watter could not coax much
volume out of the horribly inefficient Stax's, but the sound it did produce
sounded like music: refined, trimbrally correct, and within a narrow volume
range, alive. The magic of tubes and stats. Not being able to afford proper
tube amplification for the Stax's, I sold them, and proceeded to spend
several years looking for another pair,
until about ten years ago when I managed to find them.

Stax-F81. Volume and low-end limitations, but midrange that comes as
close to the sound of live music as anything I have ever heard. Even
better IMO than the Quad ESL. Mrtennis, we actually can agree ;-)

Around 1974ish I had a Sherwood receiver, Phillips TT and AR3a speakers. What was really popular at that time were reel-to-reel tape decks. So, I added a pretty good TEAC deck. Can't remember the model. The impact piece came when I went to the local Pacific Stereo store to see a demonstation of a new product by Pioneer. It was the RG-1 Sound Expander/Processor. It was meant to improve sound from tape decks. The place was packed that day and they sold quite a few. I was a buyer and I still have it.

In the late 80's I walked into a computer store here in NYC to have my MAC SE computer fixed. It turned out they also sold audio, and I saw some panel speakers in the other part of the store. I inquired if they were electrostats, since I had read about the technology in Audio magazine when I was in high school.

The salesman played what turned out to be Quad 63 US monitors with very long radio shack or low end monster cables, Quad electronics and CD. I was shocked when I heard what sounded like a live jazz trio playing right in the large showroom. I then went to listen to Quads at a true high end store, but this time with Spectral gear and MIT 330 shotgun cables. I was floored when I heard the price of the cables alone, and thought how can I ever afford such a system.

Being right out of college and in my first job I new I could not drop an entire years salary on a system. But I never got that sound out of my head.

Eventually someone told me about Audiomart and I soon entered the world of buying high end used audio, essentially recreating the system I heard in the high end store, except with Crosby'd ESL63's (which I had never heard until after I bought them)

But that original exposure to the Quads is what really opened my ears as to what was possible. In high school I had heard DQ 10's and infinity 1.5's (I think) that I wanted, but I could never get my dad to spring for high end gear, even though he loved music and played a compact stereo all the time.

Even today my ears seem to prefer point sources, and the speakers I live with (and g-d help me, now sell) in many ways sound like powerful extended versions of those original Quads. The designer, Andrew Jones, loves Quads as well, a listening preference which shows up in his designs.

I also remember vividly my first few exposures to tube amps.

I just recently met two different young audiophiles, one of whom heard my system and commented how unbelievable it was to hear what sounded like the maracas from Sympathy for the Devil playing live right in front of him.

So things have come full circle in a way. I told them both about Audiogon, and have offered to help guide them to find used or budget systems.