The NOS 6H30DR tube has been discussed at some length, but different people come to different conclusions. Some find no difference, some find a slight but insignificant difference, and some find a very important difference. So system and personal preference prevail.
Doesn't the VK75SE take only a single pair of these? I would recommend you give them a shot. I would also recommend the EAT Tube Dampers, regardless of which 6H30 tube you pick. Although the 6H30 is not terribly microphonic, microphonics are never a good thing.