I'm also not keen on the stock preamp tube. Currently I'm trying a JJ (Tesla) 12au7. I've read good reviews on Psvane so may try that as well. I do think I'll check with Rogue first.
Rogue Cronus Magnum preamp tube
After listening to my Rogue Audio Cronus Magnum for a few weeks I changed the center 12au7 preamp tube from the stock Sylvania to a Telefunken ribbed plate. I got more of the detail I was looking for but a bit too much. Is there a tube that will give me a sound somewhere in between; retaining the warmth and lushness of the Sylvania but adding in a bit more detail?