Tube Amp with tone controls for Heresy IV's

just use a schiit loki coupled with any tube amp you want

easier and more straightforward than finding the unicorn modern day tube amp w tone controls... there is a reason you are having trouble finding them...

leben cs 300, cs600 has 3 steps bass boost control

Not just finding them but for 3K or <  that sounds good too. I don't know of any integrated valve amps.. Sansui maybe, if you can find a good one to rebuild..

I'd say it's going to be an older unit, if at all, for me anyways.
New, not gonna happen, used if it's older an probably rebuilt, for my taste.

Separates, no problem.. ANY older tube Mac pre any older Mac valve amp.. They will work.. Actually made for Klipsch, JBL, Jensen and Altec.
BUT you gotta have GOOD tone control.. Not just tone control.. I like Macs, loudness, bass contour AND tone control.. all of those features (C20) make a Mac very versatile.. Takes a lot of the "tube rolling" crap out of the mix too..

Regards