Another preamp I can suggest is the Holo Audio Serene. It is very similar to the HPA4 with a tinge of warmth. It actually measures a bit better than the HPA4. I wanted to get a second HPA4 for my office system, but I thought I would try the Serene to have some variety.
It is not much different than the HPA4, but a few people have posted that they like it over the HPA4. I would not say that both are exactly what I want.
I use the Serene with my slightly brighter system,
Magnepan LRS+ speakers | Holo Serene preamp | Schitt Yggi+ Less Is More DAC | Sanders Magtech amp | Audience Front Row speaker cable | Audience Au24 SE and Benchmark XLR and RCA
I can easily replace the Holo Serene and HPA4 in either system with the other and be happy.