With the X5s I started with the Primaluna HP Premium integrated produced in late 2017 after the cap upgrade. Then upgraded all tubes and the sound was amazing. Since last March I have had the Don Sachs Valhalla in the system and as good as I thought the Primaluna was, it is no contest. The DS has more grunt, body, 3 dimensionality just about everything is better with the DS. I believe the sonic differences are due to Don's engineering skill and experience with parts that sound right as well as using 6SN7s up front. Only disadvantage with the DS compared to the PL is that I can't use KT150s in the DS and I can't switch from triode to ultralinear with the DS. Bottom line, to me, you would have to pay considerably more than the Valhalla to better the sound. I am not going to, very happy with the DS. Like Geerock and DS before the Lampi's I too use the MP-D2 DAC.