Now I get it...

Consider ultrasonic cleaner if you have not already. Especially if you bargain bin and listen to older records. You'd be surprised how much ground dust accumulates in 40-60 years. Though that dust could tell some pretty cool party stories.

Congratulations.
I have done the same thing resently. But in a much smaller scale. And it goes in waves.
I have done most of the things I could do in the vinyl playback chain. And that is a lot over several years (!).
I almost gave up. The magic were there and were gone and now it is back in full effect.
To illustrate what I have done to get there:
Löfgren B Arc protractor
Dynamic adjustment and by ear SRA
Peter S anti-scating procedure
Speed adjustment while playing
Good ML stylus and cartridge(s)
Redraw tonearm cables with pure silver wire
Replaced RCA cables with known uF fully shielded
Upgrading dedicated power supplies
3 different RIAA Amps tested
Passive pre amp with coils
Build my own power amplifiers (driven by car battery)
Pure silver dual shielded ala chord DYI speaker wire
Bookshelves upgraded with top of the line crossover components
And dual 8" sealed sub
Dedicated room with sub 300ms decay times
Treated reflections points
Base traps
All lined up perfectly to the wall boundaries

Now I lend my RIAA to a friend. I had another RIAA in the meantime that the op-amps I had upgraded to audiophile grade developed for hi-fi MUSES 01. That were superior too the original 
OPA2111KP.

But here is the catch.. I ordered fully descret op-amps to try them out. And surprise they were better than the MUSES! And the they played one octave lower than the MUSES couldn't.
But they also made vinyl playback so much more enjoyable like your experience. 

So I have not powered on my new streamer and DAC yet since then.. and just enjoy my vinyl collection for the moment.

And it took all those years as in a roller coaster to get too this point.. 

Congratulations on your sonic breakthrough!! In my experience the most common reason for a recording to sound bad is that it is not a first pressing.  That is not to say that bad recordings don't exist-there are a lot of them.  But, the least crummy sounding will be a first press, and sometimes the differences are astounding. Discogs is a great site to determine true first pressings. I truly enjoy "the hunt" in finding replacement vinyl for my non-first presses. I agree with Uberwaltz that you need to stick to EX/ NM grading when purchasing used records on line, and even so, most grading is visual and doesn't always translate into a quiet record. I agree with the advice to largely avoid reissues.  With tape degradation many have lost the magic.  The Beatles reissues however are glorious!  Ultra clean records are also a must.  Besides removing a lot of noise, a veil is usually lifted revealing more detail and a better sense of "being there". Having gone trough the entire spectrum of cleaning options, I feel comfortable stating that Ultrasonic cleaning seems to work the best, but that is a topic for another thread.  Enjoy!!

With my new set-up I am astounded about how some of my albums just make me go "Holy S***!" While the others, most often the reissue 180 gram "audiophile pressings", are enjoyable but sound less alive. There are exceptions to that rule, of course, but I think you all understand. In other words, I now finally get the value of consideration paid in searching out really good vinyl.

How right you are. You will know when you have a really fine system because everything will sound better than you ever imagined, and some really good recordings will sound better than you ever even imagined was possible. If you want to know what I mean, I highly recommend spending some time searching around Better-Records.com It takes some time to search around and you might have to wait a while for a record you really want to come up but when you do it will be worth every penny. I have several and every one of them is on a whole other level even compared to some of the best ones I had before. Or if you disagree, send it back. But I doubt you will be able to do that. I never can.

My first was Fleetwood Mac Rumours. I have an early issue original, Nautilus half speed remastered, and the 45 reissue. Tom Port’s White Hot Stamper blows them all away. Its not even close. Played the 45 for a guy one time he said, "That’s gonna be hard to beat" and then could not believe how much better the White Hot Stamper was. Its laugh out loud silly how good some of these are. Tom Petty, never even knew he had genuine demo disc quality material until I heard the WHS of Southern Accents. Nilsson Coconut is another one. Freaking insane sound quality! Hot Stampers- best kept secret in audio!

Hi @millercarbon, funny you should bring that up!  I just ordered my first LP from Better-Records, an early release White Hot Stamper of Black Sabbath's self-titled debut.  I am so excited to hear it, especially after your comments above.  Will report back once received (should be here next week). 

@mammothguy54, my copy of SRV's In Step from Analogue Productions is on the way!

To everyone else who has been responding to this post... THANK YOU!  I have thoroughly enjoyed your insights.