Audiophile Record Labels

ECM recordings are always of the highest quality (http://www.ecmrecords.com/Startseite/startseite.php). Naim also has its own label with very good recording quality (http://www.naimlabel.com/)

Reference Recordings in my opinion are some of the finest.

I have extensive experience with Telarc, Mapleshade, Sheffield Labs, Chesky, DMP, Audioquest XRCD, etc.

Mapleshade is sort of an organic type of sound.

Chesky Ultimate Test and Demonstration CD is a great tool to evaluate your system and develop good listening skills.

Telarc, DMP, Reference Recordings are all incredible!

If a particular recording is available in XRCD or XRCD II sometimes it is a huge step forward, sometimes not. For example, Dire Straits Brothers in Arms is WAY better on XRCD II while Eagles Hell Freezes Over is only slightly better and maybe not worth the $40 on XRCD II version.

(just to be forthcoming I am a dealer for Chesky and Reference Recordings)

I second anything by ECM. Consitently top-notch recordings. Mapleshade,Chesky and some Telac as well!

Add Harmonia Mundi and Bis to the list. I'm assuming that you're not going back to the early days of stereo (RCA Living Stereo, Mercury, Lyrita, etc.).

In addition to MoFi's list I would add:
The 180g Warner Bros
Cisco Music (but i think are done)
Naim
and the new Rhino label