I replaced the 12AT7s with Telefunken ECC801s. I replaced the 12SN7s with CBS/Hytron VT-231 per a recommendation from Brent Jessee. I definitely recommend reaching out to Brent. He is incredibly knowledgeable and extremely helpful.
In my system, the tube changes were a dramatic improvement in sound. There was better top and bottom extension. The sound got even more dynamic. It wasn’t cheap, but the rolling to me was well worth it.