I prefer to use purely acoustic tracks.
My favorite is "Moon Run" by Trapezoid Amazon.com: Moon Run: Trapezoid: Music
. Excellent recording, perfect balance and most of all, a most beautiful piece of music.
I also use "Liquid Amber" by Lawrence Juber - The version from the "Sounds of Wood and Steel" collection by Windham Hill Amazon.com: Sounds of Wood and Steel: Various Artists: Music
However, when trying to impress people, I use "Lilly was here" by Candy Dulfer and Dave Stewart Amazon.com: Saxuality: Candy Dulfer: Music
. Not audiophile quality since it's heavily processed, but it can sound impressive with a modest setup.
Another favorite is "Private investigations" by Dire Straits, the entire "Dark Side Of the Moon" by Pink Floyd (I have 4 different versions of this) and "Your Own Sweet Way" by the Notting Hillbillies.
For vocals I use tracks by the recently late Lasha de Sela, and the "Song to the Siren" by This Mortal Coil.
For bass, I use Massive Attack's remix of Nusrat Fateh Ali Khan's "Mustt-Mustt" (probably the best bass loaded track).
Last, there's always room for Carl Orff's "Carmina Burana" - O Fortuna velut luna statu variabilis, semper crescis aut decrescis...
Play it loud and even if the system you setup is basic, you are going to impress everyone.