I’m looking for suggestions for a tube Pre Amp

My Current System:

Benchmark USB DAC1
NAD M3 Integrated Amp
Vandersteen 2CE

For a long time I was rocking a Wavelength Brick USB Dac (which is a tube dac) as my source component, but have now moved to a Benchmark DAC1 USB. I like the idea of having a tube somewhere in my system but I don’t really think I can afford to maintain a tube amplifier. That being said, I’m considering adding in a nice tube preamp then use my NAD as a power amp only (and potentially moving away from the integrated NAD at some point).

Can anyone suggest a moderately priced Tube Preamp that would complement this system well?
Preferably used... I hate paying retail. But I would be willing to do new if there was a in-home trial offer of some kind.
Have you tried to use the DAC1 as preamp to drive the NAD? Adding an unnecessary component in the middle, be it tube or otherwise, may not be a good idea.
I've been looking at YS Audio tube preamps, as they have a true balanced design, with balanced input and output. That would work great with your new DAC. Worth a look, especially at the SE edition.