Grado SR-225 or Sennheiser HD580?

Sennheiser -- you won't be sorry.

The pads from the SR-60s deffinately help the Grados. I use them on RS-2s. -- The HD600s are worth the difference over the HD580s IMO. The lack of resonance from the carbon makes a difference. The also have considerably more bass. You really have to want to listen to Grados to put up with the discomfort level. The Sennheiser is a good choice. You can check out frequency response curves at the Headroom website -- http://www.headphone.com/layout.php?topicID=10

I have both the Grado 325s and the Sennheiser 600s, and I agree with the above. The Sennheisers are much more comfortable and I might even prefer the sound, though both are very good headphones.

I own the HD600's, and they have better defined transient response than Grado RS-2's which I auditioned, probably because of less resonance. I also found the Grado's shaded too much toward the bass. Sennheisers win easy on comfort, but the 600's need a good partnering headphone amp if the sound is not to become fatiguing with their more difficult load. For the record, even driven with my quite capable Musical Fidelity X-Cans v.2 amp, I am ultimately still not satisfied that the 600's are as tonally nuetral as I would ideally want, but there may be nothing in the price range (or even at all?) that is. Headphones are a very personal choice, though, since everyone's ears and head (physically speaking) are different, so you really must audition some for yourself.

I stepped up from the Grado 80 using the headphone jack on my Radio Shack Optimus CD-3400 to the Sennheiser 600. Everything got much better, although I might like a touch more bass. I am now using the Berning micro zotl and the sound is simply terrific. It is amazing what I can hear that is lost through any speakers. The Grado might be similarly capable, but if you can sit with the Grado on your head for two hours you are a better man than I.