When Steve Guttenberg reviewed the Sennheiser HD 650 headphones, he rightfully called them "fit for a king"--while noting that they retail for a correspondingly princely sum of $500. Thankfully, the HD 650s aren't the only model in Sennheiser's high-end audiophile line. The Sennheiser HD 600s can be bought at a 40 percent discount to their big brother. Yes, you'll be substituting a grey and black plastic finish for the 650s' fancy titanium metallic housing, but you'll still be getting a high-end pair of open-air headphones while saving enough money to buy a really nice bottle of vintage wine to sip as you listen to your music of choice. (For me, that would be the losslessly encoded FLAC version of Phish's live June 6, 1998, rendition of "Piper.")
If you're not familiar with the open-air design, they leave the outside of the ear cups open so that sound waves moving away from your ear can continue away unimpeded and cannot interfere in any way with the sound moving toward your ear. In the case of the Sennheiser HD 600s, there are pieces of black metal mesh on the outside of the ear cups to cover the drivers and protect them from accidental damage.
Speaking of those drivers, Sennheiser is happy to point out that the HD 600s use computer-optimized neodymium magnet systems, which is supposed to minimize distortion, to drive lightweight aluminum voice coils. A 9-foot Y-cable (one wire to each earcup) delivers your tunes to the drivers and is terminated in a gold-plated 1/8-inch (3.5mm) stereo minijack connection. (Sennheiser also includes a phono adapter for the larger headphone jacks that snap securely over the smaller headphone plug.) Both the earpads and cable are user-replaceable--though Sennheiser is, of course, your only choice when doing so. Replacement earpads will cost you about $41, while cables cost about $25.
Since the HD 600s aren't nearly as efficient as most earbuds, you won't get ear-splitting levels of volume out of them with a portable music player, such as an iPod. However, listening to music at such levels can damage your hearing. I typically got a comfortable volume out of my iPod with the HD 600s. However, with some recordings I did crave a little more volume from time to time. Also, given their open-air design, which lets in outside sounds, you might have trouble cranking your music to try to compete with sounds in a loud environment. I wouldn't want to use them on the New York subway or to try to drown out my dorm-mate while he practices his guitar.