Solid state or Tubes preamp phono stage.

I agree with Mulveling. 12BH7 is another tube type that is said to be a good sub for the 12AU7, which is to say, an upgrade.

Yogiboy said "5914, 5963,6189 and ECC82 are all replacements for the 12AU7 tube".  ECC82 is definitely only a 12AU7 by another name. In the case of "5914" in Yogi's quote, I think that's a typo and he meant 5814.  The open question is whether 5814 is only yet a third name for a 12AU7, i.e., the same tube with a different alphanumeric code, or actually a different tube electrically that can be freely substituted for a 12AU7/ECC82.  As to the 5963 and 6189, all bets are off so far as I am concerned but one can look up the specs in any good tube manual to see whether they are identical to 12AU7/ECC82.  I'd preferentially go with a 6CG7, provided a 6.3V filament supply and the ability to reconfigure the socket or with the 12FQ7, provided a 12V filament supply, that requires no soldering.  But both of those latter tubes may require a bit more filament current than the 12AU7/ECC82.  Most gear can handle it.  And I feel very strongly that the sound will improve.

Yes that was a typo error. BTW, my tube power amps use 12BH7 tubes and I was told from the manufacturer that I can sub a 12AU7 in place of a 12BH7.

It should be okay to try. The 12bh7 supposedly draws more heater current, but they should otherwise be pretty similar as far as compatibility. So if the circuit can handle a 12bh7, a 12au7 should be fine.

But the 12BH7 will sound better, by all accounts (see TubeDIY Asylum).  I haven't tried that type myself. Now, if the 12AU7 is being used as a cathode follower, then it does not do so much sonic damage and can probably be tolerated as is. In my own search for the "best" 12AU7, I ended up with genuine Amperex Bugleboys, because I had a few in my stash, purchased new by me in the early 80s. But even those were bested by the 12FQ7.

Have you thought of a Sutherland solid state PS? Extremely low noise floor and it will let the cartridge do the talking.

As mijostyn said, tubes are a PITA and IMHO for the equipment hobbyist (whether or not they are really into the music). Plus they can run hot.