Buy 12ax7 tube

Another vote for Psvane 12AX7-T11. Rolled them into my Vincent SA-T8 Pre. Massive jump in performance. Very bright initially, but settle nicely after 70 hours or so. Quiet, superb dimensionality, highly resolving.
And yes improving the Power going to your Equipment will help greatly.

Go to Brent Jesse Tubes and read... Tubes are heavily researched for character and tested. He stands behind his inventory.

I use Telefunken smooth plate on my McIntosh C2300 MC phono stage and Gold Lion gold plated pins, cryogenic treated for my line stage.

Check out Doug's Tubes and Upscale Audio.

+1 to Loweider57, he is spot on with all advise . At your price point Tungsram and EI are your best bet . Telefunken is the best overall . Once you go Telefunken, you’ll never go back . I have a pre that takes 2 12AU7’s . I have about $ 2500. invested in 12AU7’s alone  . From RCA to G73-R Telefunkens. The smooth plate regular grade Telefunkens are the best bang for the buck . When looking,  Tungsrams might be relabeled as RCA or Raytheon. If you want Telefunken sound but a little brighter , try the Nickel plates . Happy Hunting , Mike.