One thing I never leave home without is my iPod. I’ve now got the 160GB version with 9,600 or so songs loaded to keep me company on my travels. I also carry a set of e-Motion speakers that allow me to play music in the odd hotel room that's still not yet iPod connected.
My homes are now all iPod compatible from a speaker point of view, but in my offices in New Zealand and New York I have simple speakers. The best by far are Bowers & Wilkins Zeppelin. This company was founded in the UK in 1966 during the swingin’ 60’s and was a Lovemark for me way back when. I bought my first pair in the 70’s (as soon as I could afford them) and since then they’ve gone from strength to strength. Some of the speakers go for $60,000 a pair, but that market is drying up (I think it’s around $1.7 billion per year in total). Portable MP3 player speakers already do more than a billion dollars.
The Zeppelin remains head and shoulders above any other speaker. I don’t know all the technical stuff but I do know that the Zeppelin sounds as close to a full strength B&W system as you can get for something 25” wide, 7” high and 8” deep. Try it and you’ll never go back to any other system.