This is my sort of the thread... :D - even if I do just listen with headphones in stereo or through my TV -- I don't have the luxury of 5.1

but would love it.
For audio show-offage I can get lost in the moment

Which isn't a bad thing!
Normally when I was setting up and tweaking settings and levels, my go to disc was The Incredibles. However, as time has gone on, this has changed.
I can reccomend
Moulin Rouge (Dir. Baz Luhrmann) highly. The DVD has both DD and DTS soundtracks which are THX approved, both of them sound fan-amazingly-tastic through headphones, and I remember at the cinema it was just

- in a good way! Like nothing I'd heard before in a film.
Zhang Yimou's wuxia tour de force that is
House of Flying Daggers is an all round sensual treat. However, I'd like to direct you to the
Echo Game scene, the first time I saw it, I was breathtaken (seriously) and on repeated watches it only gets better. The soundstage throughout this scene and the following scenes is just pure cinematic mastery.
Also, you can do worse to check out
Michael Flatley's Feet of Flames (Dir. David Mallet) There is great fidelity throughout, considering there is alot going on at times with the band and the taps, it's very enjoyable. This may not be an obvious choice, but you may be surprised.
Music choice now -
Tommy Emmanuel - Center Stage (Live) - His finale piece Initiation will knock your socks off. It sounds AWESOME in stereo and on the CD, so having it in 5.1 will be a treat I'm sure. If the CD is anything to go by, there will be a tonne of bass and just great clarity throughout.
Hope that helps!