6h30 tube

I'd give 6n6p tube a try. I use them in my BAT preamp with excellent result.

They made a difference when I tried them in a CJ Act pre, they were worth the money to me.

This subject has been addressed several times in the archives. IME, NOS DR sounds better in VK75SE, but after 1200 hrs. an aged DR is surpassed by a fresh EH or Sovtek. There are relatively simple & inexpensive mods that can be done inside chassis to greater effect than DR tubes.

The 6h30 dr's seem to have a bigger impact(improvement)when used in preamps as oppose to amps. Personally,they were a big improvement in my LS-25 mkII as well as my friend's LS-26. They have a life expectancy of 10,000 hrs.
I had the exact opposite experience as Dgarretson. My 5yr. old Bat 6h30dr's sounded much better than a brand new pair of EH 6h30pi goldpins.
The only way you'll know for sure is to try them yourself in your system but at the price they're going for now, it is an expensive endeavor.