Tube selection is very subjective. I don't know anything about your guitars, playing style etc. So ....
I will make some assumptions .... hopefully some of them correct....
Since you were attracted to the Empire I will assume that you like the tone of the great Marshall amps. I love Marshall amps myself but once the master volume was a part of the design my like for them declined. My favorite models are the four input / non-master models and this is one of the amps the Empire can replicate really nicely.
The output tubes in these amps are JJ 6V6 tubes. I normally am not a fan of JJ 6V6 tubes in 6V6 amps as they sound and react more like a 6L6 than a sweet 6V6. They are too aggressive and more edgy than a older era 6V6. But ..... in the Empire they may be the best choice. Dan Boul had no intention of making a Fender BF Deluxe when he created the Empire. He wanted to cover the tones of the great Marshall era. A sweet 6V6 would not have filled the bill in the same way as the JJ. Bottom line after all my rambling .... you can leave your output tubes alone
Preamp tubes ....
If it were my amp I would use a medium plate or long plate in V1 as did the Marshall amps of the era. The JJ803S and/or Sovtek LPS are medium plate tubes and work fine but if you grab an NOS Mullard, GE, RCA or Sylvania from the 60s or 70s you will hear things that were not there before. More articulate, more defined, more responsive.
Let me know what is in the phase inverter as it could be an LPS or 803S and I can give you an idea or two. Let me know your most commonly used guitars and I can give you a few phase inverter ideas as well.
The Empire is a pretty cool piece of work. Happy playing.
Thanks for the info and quick reply!!! I mostly play Les Paul and ES 335 style guitars with Humbuckers and I play mostly blues/Classic Rock primarily rhythm guitar. I am not familiar with the tube layout and function for the Empire and can't find the info anywhere. I assume that V1 is the one closest to the face/seperate and that V5 would be the phase inverter. That said V5 has a JJ 803s in it and V1 has a JJ 803s. The others are Sovtek and EH 12ax7's.
Here is some of what I have already if any of them would work. I have one very expensive Pristine Cryo treated NOS 1962 Raython Blackplate 12ax7 that I got from tubeworld perfectly matched at 2.2ma with MU=110+ that I have been saving for use as a PI. I also have a NOS JAN Phillips 5751 and several of the new Canadian (imported from china) Northern Electric 12ax7's from the Tube Store and some Genalex 12ax7 Gold Lion Reissues.
Hopefully that helps give a clearer picture. Once again Thank you so very much, you are a living treasure. If there is anything I can do to pay it forward let me know.
