An update:
Over the past months, partly due to tube advice given in this thread, I have been enjoying my Einstein The Tube Mk2 preamplifier a lot. Or more precisely, I don't feel I have a preamp problem anymore, and don't worry about it. It fills its role fine.
It does have a bit of solid state sound I suspect, but I am not much bothered by it, after the NOS tube upgrades (described above), and its assertiveness fits in nicely with the rest of my system and fairly large room.
A special treat, for me, is the ability to mix it in optimally. Since I have volume on the Aesthetix Io phono preamp too, I can mix and match. The sound is fatter and more organic with the Io taking most of the amplification load, and leaner and more precise with the Einstein taking most. A nice dialogue indeed. I like to have the Io volume at three o'clock and the Einstein at twelve or one o'clock, to get the best sound. This preamp is certainly delivering, and even if it was expensive, I got it more reasonably second hand, and am glad I bought it.