Another headphone amp I recently found out about - and have since added to my system - is the spl Phonitor X, which falls $400.00 U.S.D. above your stated price limit of $2,000.00.
What makes this headphone amp stand out for me is its analog matrix system which recreates the effect of listening to loudspeakers on your 'phones. It does this by feeding a discrete low-level, listener-adjustable, signal from the right channel to the left ear, and vice-versa, from the left channel to the right ear, to overcome the total LEFT-RIGHT separation of stereo channels that headphones otherwise impose upon our ears. When you’re listening to a pair of speakers, some of the sound from each speaker reaches the opposite ear, filling in the void headphones create. The matrix overcomes this void.
spl’s rationale for including the cross-channel matrix is based on the fact that, according to spl (Sound Performance Lab), most recordings are mastered for loudspeaker, not headphone, listening. The cross-channel matrix feature can be switched completely out of the headphones circuit, allowing you to fully compare the two ways of listening. Some recordings sound better with it off; others, far better with it turned on; I am finding that extended listening to recordings with the matrix activated is far less fatiguing to my ears.
I have had this unit for only one week, and I’m already totally taken in by how much more natural-sounding recordings are over my headphones (I have Focal’s Utopia and Sennheiser’s Model HD820 headphones). It sounds very good to my ears already - clear and transparent - and will likely improve even more after an extended break-in period.
Yet another feature the spl matrix offers is the ability to adjust the perceived angle and distancing-apart of loudspeakers when you audition a recording. The Phonitor X comes with standard and 4-pin balanced headphone jacks, and has plenty of reserve power to drive nearly any headphone.
Here is a link to one review of this unit: https://www.headphones.com/blogs/news/spl-phonitor-x-review