what are the "must have" CD's


For years, I've invested in quality sound equipment and have a small collection of CD's of different types.....but I realize that there are problaby some "must have" CD's that really show just how good (or bad) a system really is. This isn't a quest for who your favorite female singer is...or what orchestra you like the best....I'm really after sonic quality and sonic range (gotta show off the sub and boomy rock probably isn't the best way to do it).

I'm open to suggestions in most any musical category...the only qualification is that the CD has to be readily available and not some collector's item.

If there is already a list somewhere..please point me to it....or post your suggestions.
ghstudio
These discs are sure to put smiles on the faces of your guests and all of the music can be enjoyed and understood by many.

Mannheim Steamroller "Fresh Aire Seven"
Diana Krall "Loves Scenes"
Sade "The Best of Sade"
Nils Lofgren "Acoustic Live"
The Rippingtons "Curves Ahead"
Natalie Merchant "Tiger Lilly"
k.d. Lang "Drag"
Shawn Colvin "Fat City"
I like the music from mercedes soza, one cd that is a must have in any collection, is "Live in Argentina".
Nice recommendations provided by all. I would add the following to your short list of must have recordings:

Diana Krall - All For You (Tribute to Nat King Cole)
Donald Fagen - Morph The Cat
Seal - Greatest Hits 1991-2004(Acoustic Version)
Mary Stallings-Live at The Village Vanguard

The last two are hard to find but worth it:
Johnny Adams - One Foot in the Blues (INCREDIBLE, great dynamics, the best for testing your equipment)
Prince-Just One Night (box set, live)
Since there's some interest in "Americana" here, let me recommend "Heartworn Highways," a collection of informal recordings of some of the great Texas bards (Clarke, Earle, van Zandt), back in the day (mid 70s).

Great songs, and though the recordings seem to vary a bit across tracks, the sound is wonderfully natural. According to Stereophile, who named it a "recording to die for" the recordings are somewhat low tech; anyway, it really works. Highly recommended, if you like male singer songwriters.

John
Willie Nelson's "Moonlight Becomes You". Excellent great sounding renditions of several very classic standards. Simple, basic, accoustic, and very live sounding. A first rare recording.