Please help me educate myself!

[Daverz]

My sarcasm detector is very acute, but for now I'll treat this as a sincere comment. Let me know if I'm wrong to do so!

Trust the detector.

[Ken B]

I suggest subscribing to a streaming service. (Qobuz is probably the best if you can live without Naxos, Hyperion, ECM and MDG, but I freely admit my prejudice against Spotify is irrational.) Best way to listen to lots of things without spending lots of money. That or find a really well-stocked library.

I am pondering paying Spotify each month. Why is Q better?

Never mind, I found out. Fewer distracting choices, less music to have to consider, faster browsing of what's available. 

[amw]

I like the interface better and find it easier to find things. You also get lossless sound quality (and it's easy to download things direct if you like doing that—some of which are 24-bit, though that's usually more expensive). Spotify probably has more music though, so it comes down to sentiment.

[king ubu]

BACH: Sonatas & Partitas for Solo Violin - Szigeti (Vanguard)
MOZART: Piano Concerto K 491 - Rubinstein/Krips (not sure how to get this, I've got the big Rubinstein box)
SCHUBERT: Piano Sonata D 960 - Schnabel (part of the Schubert Music & Arts box by Schnabel)
BEETHOVEN: Piano Sonatas - Schnabel (there was an EMI box, but I guess the Music & Arts discs are preferrable)
MOZART: Piano Sonatas & Concertos - Schnabel (Music & Arts box)
MOZART: Piano Sonatas - Maria João Pires (Denon/Brilliant)
CHOPIN: Nocturnes - Arrau (Decca/Universal)
MOZART: Violin Sonatas - Grumiaux/Haskil (Philips/Universal) and/or Szigeti/Horszowski (Szell on a few, Vanguard)
BEETHOVEN: Violin Sonatas - Francescatti/Casadesus (Sony) and/or (no hi-fi!) Szigeti/Arrau (Vanguard)
BACH: The Well-Tempered Piano - Friedrich Gulda (Decca/Universal)

Szigeti/Bartók: Sonata Recital (Vanguard) - best "Kreutzer" sonata ever?

not sure how it all works for you, but you might also be well-served by some box sets such as the EMI "Icon" ones by Jascha Heifetz, Michael Rabin, Dinu Lipatti, Nathan Milstein, Alexis Weissenberg ... those worked very nicely for me when I was starting out exploring classical a bit more than two years ago!

there's much more of course, but this already looks like overkill ... and no, I don't only listen to old recordings, but the ones above are amongst my "staples", my "bread and butter" ...

[Papy Oli]

A couple of personal favorites :

Arvo Pärt – Kanon Pokajanen (ECM)
Tallis – Spem in Alium / Salve Intemerata – Summerly / Oxford Camerata
Pergolesi – Stabat Mater – Alessandrini / Concerto Italiano
Byrd – Mass for 4 & 5 voices - Summerly / Oxford Camerata

[North Star]

A couple of personal favorites :

Arvo Pärt – Kanon Pokajanen (ECM)
Pergolesi – Stabat Mater – Alessandrini / Concerto Italiano

Howdy, Olivier!
I definitely second that Pergolesi / Alessandro Scarlatti recording.
I don't know that Pärt disc, though. I absolutely adore Pärt, and the Fratres disc on ECM in particular. Well, the Arbos disc, too - but I haven't even managed to buy it yet, and I've been meaning to for a couple of years..