According to my personal experience, it makes not much sense to mix class D with tube preamplification. While class D may give a clear very low distortion sound, tubes would always add a notable (for me) distortion that ruins class D clean sound. I prefer to use either pure tube setting or pure SS setting as I enjoy both kinds of sounds. Mixing tubes with class D gives some extra warmth but also a notable distortion which, for me, they are not compatible.
And one more vote of PS audio Stellar S300. I use it in my third system with PS audio Gain Cell pre. I use this system not very often. Each time I return to it, it sounds better. They took quite a while, far above 400 hours, to come to the sound of that quality, which is clean alive and presential, live recordings sound especially good, the base it tight, mid and high frequencies, dynamics are fine, there is nothing to complain about, especially for the price. The difference as they sounded at the beginning and now is just drastic and the sound is still getting better. My initial confusion was also caused by the DAC incorporated into the pre, which is not indeed good I use now an external one. It is a rear case when one gets completely satisfied with what he has.
And one more vote of PS audio Stellar S300. I use it in my third system with PS audio Gain Cell pre. I use this system not very often. Each time I return to it, it sounds better. They took quite a while, far above 400 hours, to come to the sound of that quality, which is clean alive and presential, live recordings sound especially good, the base it tight, mid and high frequencies, dynamics are fine, there is nothing to complain about, especially for the price. The difference as they sounded at the beginning and now is just drastic and the sound is still getting better. My initial confusion was also caused by the DAC incorporated into the pre, which is not indeed good I use now an external one. It is a rear case when one gets completely satisfied with what he has.