The Sennheiser 600 is a great value, comparable in sound quality to the two wood-bodied Grados (can't recall their model numbers), at a slight sacrifice in build quality, for a significant reduction (percentage-wise) in cost. If you aren't also buying a headphone amp, you aren't doing these units justice.
An alternative at least worth looking into (if it is still in production) is the Koss electrostatic (ESP950, if memory serves), which comes with its own power unit. Sound quality is in the same league as the above, with the usual electrostatic pluses and minuses (surprising air for a pair of headphones, but a coolish bias). Not the same build quality as the 600 or the Grados, but a lifetime warranty (which Koss just cheerfully honored for me MANY years after purchase).
An alternative at least worth looking into (if it is still in production) is the Koss electrostatic (ESP950, if memory serves), which comes with its own power unit. Sound quality is in the same league as the above, with the usual electrostatic pluses and minuses (surprising air for a pair of headphones, but a coolish bias). Not the same build quality as the 600 or the Grados, but a lifetime warranty (which Koss just cheerfully honored for me MANY years after purchase).