My two cents...
I've owned Grado Reference headphones, and I now own a pair of Sennheiser HD580s, a pair of Sennheiser HD600s, and a pair of Etymotic ER-4s's with custom-fitted earplugs. And a long, long time ago, I owned a pair of Stax Mark III electrostatic phones (stolen in the '70s ... sigh).
I sold the Grados after I got the 580s, because the Senns kicked their hiny. I gave the 580s to my son after I bought the 600s (new on eBay for $215) because they were noticeably better in every way -- deeper, smoother bass, sweeter, airier highs, and more transparent mids.
I don't use the Etymotics much, because they're a pain to put in and because I don't monitor while recording in the field. They're great on airplanes, though. They're definitely thin on thin the bottom compared to other great phones, but excellent overall.