+1 for Grados. I'm a big fan, as they are very dynamic headphones that I find pair well with my Mainline amp. My favorite Grados are the limited run of GH2's from the Heritage Series. They used cocobolo wood in their construction and are very detailed and musical, but also difficult to find. The new RS2x is also a favorite of mine, and I really like my SR325x's with the Mainline. I haven't tried the higher end Grados.
I have also owned several models of Audeze headphones and they work well with the Mainline. The LCD 2's are a bit on the warm side and are very good, but I preferred the more detailed and neutral LCD X's. My current Audeze cans are the LCD XC, as I needed a closed-back headphone for use late at night when the rest of the family is sleeping. I like them the best of all the Audeze's I've tried. They are a neutral headphone, but I still find them very musical and easy to listen to.
Good luck in your search!
Scott Burgess
BeePre 2, Kaiju, Eros 2, Rega P6, Rega Apollo CD player, Bryston BDA-1 DAC, Bryston BDP-1 streamer, Jager speakers, Mainline and Crack for headphones.