For which headphones? I can only speak for the combination I use, which I'm very happy with: Violectric V181 with Audeze LCD-2's is an excellent combination. You might also try posing the question over at Head-Fi.org. I might include the headphones you are intending to pair the amp with though.
Best solid state headphone amp under $1000
I'm looking to upgrade my channel island VHP-2 to another solid state amp under $1000. Here are the contenders that I can think of. Let me know if you have compared any of these directly, which is the best in your opinion, or is there another you would suggest.
headamp GS-1
stello HP-100
burson HA-160
PS audio GCHA
lake people HPA V181
blue circle hat peed thingee 1 or 2
rudistor nx-03
graham slee solo
musical fidelity M1HPA
headamp GS-1
stello HP-100
burson HA-160
PS audio GCHA
lake people HPA V181
blue circle hat peed thingee 1 or 2
rudistor nx-03
graham slee solo
musical fidelity M1HPA