Tube DAC or Line Driver?

I have active speakers (BeoLab 8000) and I’d like to put a little tube love between the output of my preamp (NAD M12) and the B&Os. There’a a ton of tube preamps out there obviously, but I’m looking for one with a DAC front end & do not need switchable inputs or even volume control. The NAD can deliver either Optical or Coax but not USB. I am prepared to undertake a project as fairly handy with a soldering iron and have built tube gear before.

Any recommendations or thoughts?