What are the "Must have" LP's?

In addition to the wonderful suggestions above:

Hank Mobley "Soul Station"
Lee Morgan "Candy"
Louis Smith "Smithville"
Sonny Rollins Blue Note 1542
Mobley Blue Note 1560
Fred Jackson "Hootin' and Tootin'"
Clifford Brown Memorial Blue Note 1526
Kenny Burrell Blue Note 1543
Any Ben Webster
Any Don Lanphere on Hep Records

Just a few, time is short, Happy Holidays!

Black Uhuru - The Dub Factor

One can never tell if you will like the music, but this WILL show off a systems capabilities, more vigorously than any other that I am aware of. A must have for me.

If I may, I'll add a few of my favorites:

180g Reissue from Acoustic Sounds:
Sonny Rollins - Saxophone Colossus
Bill Evans Trio - Sunday at the Village Vangard
Creedence Clearwater Revival - Any of the reissues

Reference Recordings (45 rpm) Out of print, but available used
Mickey Hart, Airto, Flora Purim, et al - Dafos
Respegi/Pacific Symphony - Church Windows

Mobile Fidelity
Grateful Dead - American Beauty

Sheffield Labs
Stravinsky/LSO - Firebird

Classic Records (RCA reissue)
Mussorgsky/Reiner/CSO - Pictures at an Exhibition

United Artists
Nitty Gritty Dirt Band - Dirt Silver and Gold (3 LP set, out of print, but I just picked up a very nice used one here on the 'Gon) Well worth tracking this down.

Dire Straits - Love Over Gold

Mark Knofler(sp?) - Soundtrack from Local Hero

Pete Townshend/Ronnie Lane - Rough Mix

Tangerine Dream - Rubycon

All of CAN and its members, all of VAN DER GRAAF GENERATOR and PETE HAMMILL solos, all of PAT METHENY, all of KING CRIMSON and its members, all of FOCUS and YAN AKKERMAN, all of PIERRE MOERLEN, all of PEKKA POHJOLA, all of DAVID SYLVIAN, FZ JAZZ FROM HELL, FZ UNCLE MEAT, FZ JOE'S GARAGE, FZ ZOOT ALLURES, FZ HOT RATS, all of LAURIE ANDERSON, all of MIREILLE MATHIEU, all of PATRICIA KAAS, all of GUESCH PATTI, all of GINGER BAKER...

Here are three great albums, both musically, and to show off your system:

Jazz at the Pawnshop.
Muddy Waters Folk Singer.
Cowboy Junkies Trinity Sessions.