According my computer, these are the most listened to tracks I have, so I suppose they're my favorites. So if I was auditioning a new system, I'd probably use them.

No order, other than alphabetical.

Azura - 808 State, Don Solaris
Le Voyage De Penelope - Air ,Moon Safari
Beck Pressure Zone -Beck, Midnite Vultures
A Dream within a Dream - The Beloved, X
Under the Influence - The Chemical Brothers, Surrender
Voyager - Daft Punk, Discovery
Half Step - DJ Food, A Recipe for Disaster
Racing Green - High Contrast, High Society
Pounding - Doves, The Last Broadcast
Disgraceful - Dubstar, Disgraceful
Going out of My Head, Fatboy Slim, Better Living Through Chemistry
Slider - Future Sound of London, ISDN
Supervixen - Garbage, Garbage
Yours for the taking, Gene, Libertine
Black Cherry - Goldfrapp, Black Cherry
Transmission - Joy Division, Substance (Best of)
Trans-Europe Express - Kraftwerk, Trans-Europe Express
Inspection (Check One) - Leftfield, Leftism
Vision Incision - Low Fidelity Allstars, How to Operate with a Blown Mind
She Makes My Nose Bleed - Mansun, Attack of the Grey Lantern
Group Four - Massive Attack, Mezzanine
Absent Minded Friends - Moloko, Things to Make and Do
Retreat Wicked Man - Monkey Mafia, Shoot the Boss
Sweet Smoke - Mr. Scruff, Trouser Jazz
Freedom Fighters - The Music, Welcome to the North
Jetstream - New Order, Waiting for the Sirens Call
Crystal - New Order, Krafty
Funny Break - Orbital, The Alltogether
Whirlpools End - Paul Weller, Stanley Road
All Mine, Portishead, Portishead
Orange Crush, REM, Green
Exit Music (For A Film) - Radiohead, OK Computer
In Space - Royksopp, Melody AM
Burnt Out Car (Balearico Mix) - St. Etienne, Casino Classics Disc 2
What Difference Does it Make - The Smiths, Singles
The Wild Ones, Suede, Dog Man Star
Young Savage - Ultravox!, The Island Years
Tears in the Rain - Vangelis, Bladerunner OST
Destiny - Zero 7, Simple Things

What headphones are you getting? I have a pair of Sennheiser HD-570's and they work just fine off the headphone output of my amp or my laptop. IMO, you're throwing your money away buying a valve headphone amp, and at that sort of price, i'd be surprised if it was any good. What will you be driving the amp with?