Three labels not yet mentioned, (I don't think) ...
Reference Recordings -- audiophile recordings mostly using HDCD technology; most have superb sound quality.
Analekta -- specializing in Canadian conductors and musicians, e.g. Jeanne Lamon & The Tafelmusik Baroque Orchestra
Atma Classique -- another specializing in Canadian performers, e.g. Yannick Nézet-Séguin & Orchestre Métropolitain du Grand Montréal.
I second Reference Recordings
, I like their LPs the best followed closely by the three SACDs they have released so far. Also their 176.4kHz HRx's are great but very pricey. Their 96kHz and 88.2kHz hi-rez downloads from HDTracks are a much better value and sound almost as good. Heck I even love their MP3's. Reference Recordings is a top label for both Classical and Jazz.
I would also like to add The Concord Music Group
which includes my favorite record label: Telarc
. They have quit releasing SACDs possibly because the USA no longer has a pressing plant. Since all the Concord Music Group labels still record in high resolution and Telarc and Heads-Up still records in DSD multichannel, I believe in the future some type of multichannel high resolution will be available from Concord Music Group. In the meantime some of the Concord labels (not Telarc yet) are available in 2 channel stereo hi-rez 96kHz downloads from HDTracks.
Currently new Telarc recordings are only available on CD and MP3 from the Concord website. There are many Free 320kpbs downloads
as well as Videos and Podcasts.
The only Atma I have is an MP3 download of my favorite work by Johan de Meij Symphony No. 1 "The Lord of the Rings"
René Joly, Ensemble Vent et Percussion de Québec. The music is fantastic though I am not very impressed with it sonically.
I haven't tried Analekta yet.