Schiit Mjolnir 2, Lyr3 (briefly), Meridian Prime DAC/HA, Beyerdynamic A20, Creek OBH-11.
I bought the Encore first, and added the Kenzie. The Kenzie replaced the MJ2.
Tubes are fairly easy to get, and are not expensive. I bought the second one because I liked the first one so well, and tube interchangeability was a plus. Build quality is excellent.
I also have a Headamp GSX-mini solid state. The Kenzies don’t have a lot of output power, so keep that in mind with respect to your headphone pairing.