Yow... a new forum...this could be fun!
Since I appear to be somewhere near the first non-moderator posting here, I'll start with my favorite CD for playing first every time I set up a new system or after moving or major alterations to one of my current systems (bedroom, livingroom, study or HT).
Long, long ago, probably 1986 or so, I bought a Mobile Fidelity Sound Labs CD ("Original Master Recording", gold CD surface, goofy jewel case mechanism and all) of Pink Floyd's "Dark Side of the Moon" album. My vinyl copy (which i still have, one of the first record albums I ever bought, back in 1979) wasn't sounding so good with a few scratches, so I snapped it up.
After thousands of plays, Dark Side of the Moon is still my favorite rock album. And it utterly, totally rocks my world when played through my vintage Polk Monitor 12s.
MFSL is now sadly out of business, but I've been able to find a few more of their discs at the used-record stores. They were fanatics about music reproduction, and it shows. I've picked up a few more of their CD's from used-record stores, even though they get marked up a bit because of their slight rarity.