My first pair of quality headphones were Grado SR-60. I was completely blown away by the detail they revealed compared to the types of headphones that came stock with PCDP's and DAP's. Then I bought the DT880 (older model) and I could not believe my ears. As one reviewer once said, "the headphones don't sound like anything at all," and that is a huge compliment for this type of neutral, analytial, detailed sound signature-type headphone.
I consider my DT880 to be my "reference quality headphone." It is the headphone I use to compare all my new headphones, amps, DACs, etc. When I went to my local store to shop for a headphone amp, I brought my DT880's in their ridiculous-looking metal box, to ensure that the amp would sound good with MY headphones. These headphones are definitely keepers -- even though I'm currently seeking more fun, colored sound signatures in my new head-fi purchases, these Beyers will always be the "measuring stick" to which they'll be compared.