I just put some Herbie 09's on my 6922's in a BAT Vk300x Integrated and also in a BAT VK-D5 tube CD player. I'm not sure how much difference I heard since the gear was still relatively new to me. But I am getting a 3-D soundstage with amazing space, air and instrument placement. I believe all those attributes improved with the Herbie tube dampers. The pricepoint is sweet enough that I am going to just leave them on. The Amperex tubes I am using deserve the very best!
If my Audiophile listening club wants to scrutinize the tube damper tweak some night, I'll do an A-B test with, and without them and ask the group to report on what differences they hear.