ModWright Tube Buffer

I can’t answer directly as I’ve not owned one. But if you buy one used ( $2500 single ended / $3000 balanced ) it is not cost effective. Plus they have JJ tubes and you’ll probably drop another $500 tube rolling plus an extra pair of interconnects and a power cord. If I were in your position I’d buy a nice tube integrated amp like a Prima Luna or a Rogue ( Rogue is more SS sounding ) or one of the dozen nice integrated amps at the $3-4K used range. Or sell the Yamaha and get a used Coda or Luxman integrated. I think you’d be happier in the long run. Now if you can get a tube buffer for under $1K that would be worth considering. Cheers , Mike B. 

If you want to get serious about a tube buffer -- https://spl.audio/en/spl-produkt/tube-vitalizer/.

I used one for about three years.  In use it can be complicated or quite simple.  It's balanced input/output only.

I had the original Musical Fidelity tube buffer back in 1996.  Excellent build quality and made in England.  I think it was $200.00 if I recall and had a cool design.  
 

It didn’t hurt the sound at all, but also didn’t make any appreciable positive difference either.   It was certainly cool looking though.   I ended up selling it along with the matching Musical Fidelity X-DAC a few years later.  

I have a high quality SS, tempted to try the Analog Bridge. 

I have a similar product the Gold Note Tube 1012 and it does a great job adding tube flavor into my stack. I have used it with a full stack Gold Note Pre, Phono, Amp as well as with non-Gold Note components, but of course it works better with the all Gold Note stack. I the complete Gold Note stack.