Tube Buffers worth it?

In my experience with the MF, they don't make an improvement so much as change the character of the sound. That's strictly a matter of personal taste. If you want tube sound and an improvement as well, a better (but far more expensive) move would be to upgrade to a tubed preamp.

I guess if someone had edgy solid state gear at the budget end of the spectrum, it might make sense. But in your case, I question the wisdom of sending the signal through yet another device and set of interconnects in search of an "improvement."

...But of course, people don't use it for its so-called intended purpose. And in fact, if a solid state device were marketed to perform the same function, it would sell in the single digits.