Schiit Audio headphone amps

 My Valhalla 2 has been reliable and nothing less than impressive with the supplied original tubes for the last Five Years. 
My Mjolnir is my only other Headphone Amp for a reference for comparison.
And the Valhalla 2 compares very favorably. $350 new ...
Planar HCD-X and HD 700 Can Sets.
And do not let Schiits reluctance to jump into the fray about Upgraded Cables deter you in a quest for sonic excellence.

I have the Schiit Vali 2 and it sounds plenty good with my Audioquest Nightowl headphones. I also have an older Benchmark DAC1 and it as good, if not better.

I have not tried many other headphone amps but it works pretty flawlessly. I also changed out the tube to try another flavor. You really cannot got wrong here under 200 bucks. I also you use at as a preamp for some powered monitors and the only issue is that the left and right channel are not at the same level at super low volumes, but that's the result of the volume pot used. 

I suggest you go the HeadFi forums if you want lots more detailed feedback. That is where the headphone gurus are at.

It depends on what headphones you’re driving, so would be helpful if you could share that info.  That aside, the Cavalli Tube Hybrid is also a highly-regarded budget amp with a less crappy name.