Test CD s, which ones to get.

Easy: any of Stereophile test CDs to check that your Left channel is Left...
Then the last chapter of "Get Better Sound" and CD "The Chieftains. tears of stone". If you do not want the torture of listening to Diana Krall and Joni Mitchell while tuning up your rig, then use Symphony No.3 by Gorecki (Electra Nonesuch 979282-2) while looking at Stereophile Buyer's Guide 2008, page 221). PM me if you need a copy of that article 

XLO/Reference Recordings disc. Check RR website.

Excellent discs- sevs & ptss

The best test discs imho are;
- PAD Luminist system enhancer cd
- Isotek Ultimate system setup disc
- Granite Audio Ultimate low bass test cd (particularly useful to dialing in subs).
All the above cd's work well & are safe to use if the instructions and common sense are followed.

Depends on what you’re trying to do. For setting up speakers the best is the XLO Test CD, using the track with Out of Phase info. "Listen to my voice. It should be coming at you from all around the room." When you get the best non-coherent surround sound effect after experimenting with speaker location as well as room tuning devices from the Out of Phase track you’ll get the best coherent stereo from tracks on CDs that are In Phase, which as fate would have it are not that abundant. May the force be with you. 😳