Best solid state headphone amp under $1000

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.

I have a pair of AKG 701 earphones that I'm using with a Schiit Audio Valhalla headphone amp with VERY nice sounding results. Before this I had a Musiland MD-10 DAC/Headphone amp and the music was very cold, and lean sounding. Seemed like everything had a metallic edge to it. The Valhalla was quite nice for way under $1000. Now the Valhalla is tube based but Schiit Audio does have a SS headphone amp called Asgard that you could take a look at.

good luck with your search.

I'm using it with a pair of audio technica ath-m50s, but am thinking to upgrading to a higher end sealed can, most likely Denon AH-D7000 or AT ATH-W1000x.

LLANO S-200 , very dynamic , loads of power , 2 Ohm stable , Tube like mid and highs. very simple two stage gain topology.