There’s a 99.99% chance that they are much better, than what you got with your preamp, without exaggeration. It appears you have an ear for sound. I’m simply offering an opportunity, to hear what’s available, without spending any money, outside of the postage to return them to me, after you’ve experimented. Call a couple tube vendors and ask them about 1960 to 1962, Amperex, Navy 6922s(gold pins).