If I was going to buy one of Schiit's budget models, I would opt for the Magni with its much lower output impedance. (Magni 0.1 ohms, this amp 6 ohms.) I'm not that attached to tubes, especially long-out-of-production scarce soldered-in ones. Using the general >10:1 impedance guidelines, this amp might be best with headphone impedances >60 ohms, meaning not such a good choice for low impedance cans like Grados etc. Probably no issues with 100 ohm and higher impedances.
For a newbie in headphones with a JVC HA-RX900, 64 ohms so either would work, would you still recommend the solid state unit? The power is a little under 1 watt compared to about 400mW with the Vali. Presently using the onboard head amp on my Audio GD 12 DAC, 2 ohm output, about 1500 mW with the 64 ohm JVC's. Would I benefit from purchasing one of these units or do I need to move upmarket for real improvement.
Of course the first question is how does what you have now sound. PDG, excellent bass, mids, highs, soundstage is expansive, detail is startling compared to speaker systems, but I have little except the Magnolia room at BB to compare to, and the various speakers I have. Darn I wish I had spent some time in the headphone room at Capfest last year. To put a picture to it, I'm not listening to the system, I'm listening to music and forgetting I have phones on. How much better can it get?