First I must admit ... (I know the BH crowd LOVES Sennheiser - don't get angry) ... but I can't stand Sennheisers! They are very detailed but flat as a board and unemotional. Sorry, just my take. I am a fan of Grados and have had a pair of SR60's for years. I was at AXPONA this past year and heard the Oppo PM-2 and was impressed! I also heard the HD-800's on the Firefly and it was OK.
In a moment of weakness I broke down and bought some GH1's this week. WOW! The treble detail is equivalent to the RS1 but the bass is better than all of the RS-series. It makes my SR60's almost un-listenable now. Definitely full of emotion. Listening to "My Beloved Wife" by Natalie Merchant gives me goosebumps as her voice breaking as she breaks down is almost like she is sitting next to me on the verge of crying. I read on Head-Fi to put some G cush on them and they fall between the PS500 and PS1000. Detail is slightly better than my Pass fed Klipschorns but then they are right next to my ears.
Anyway, VERY happy with mine! If anyone is looking for a set of Grados, check them out! The only downside is the build quality is between the Prestige and Reference line but the sound is between the Reference and Pro lines. And like all other Grado phones, they are uncomfortable until they break-in (band and cushions).
I also picked up a set of used Crackheadphones for use with my Crack + Speedball when it arrives.
I am running the Grados on a Richard Marsh Class-A amp.