Sonic Frontiers Line 3 "SE" upgrade - worth it?

I wouldn't be able to compare a regular Line 3 and an SE because I had mine originally built to the SE specs before they were available and have only known it this way. About 6 months or so before the SE upgrade was introduced my dealer told me about all the above (SE) upgrades he had had SF do for his personal unit [and it sounds much better....] so "why don't you do the same..." which I did. The only significant differences from your $899 upgrade is that mine came with 12 x Valvo ECC88's [instead of the Teslas]; Rel-Cap interstage coupling capacitors; and instead of the Kimber wire I use all Harmonic Technology speaker wires and interconnects so I had all the input and output wiring changed to silver Harmonic Technologies.Oh, and I paid more than the $899 to have it done! But it has been a really wonderful staple in my system. I can't praise its virtues enough and couldn't be happier without investing a lot more. I'm sure there's plenty out there these days which are exceptional too, but when you factor in all its features, user friendliness/versatility in addition to its sound... (not to mention build quality and reliability), it makes for a formidable piece of equipment. That all said, if I were you I would probably ask about the price difference if you chose to use your own tubes, it's worth the inquiry.My vote is "it's so much pre already, it's still worth putting a little more $$ into..". IMHO. Good luck.Happy Lissnin.

It would be worthwhile to find out the vintage of the Tesla tubes and, if they will do the upgrade without them, what is their value.
It was suggested to me the pair of tubes that have the most impact on sound quality are those at the LV1 and V2 sockets.
You could experiment with that, if you haven't already, by using less expensive tubes in the other four pairs of 6DJ8 type sockets and save your premium tubes for the final output stage.
Rather than spend $900 on the SE upgrade, you might want to consider what I did. Put that money toward a Placette Passive and compare it in your own system. I purchased mine used and could easily sell it for what I paid. If you buy a new one, you get a trial period with no risk. The Passive replaced the Line 3 SE in my system and it's a keeper.

Caddock & Vishay bulk foil and Holco resistors -- definitely would be better than the stock.
SPECIAL EDITION faceplates -- it might be worth to have

tube socket upgrade is not needed
kimber wire is not needed
MultiCap RTX polystyrene is not the best
NOS Tesla ECC88/6DJ8 from the 70s are better than sovetk but I'm not sure if that's what you are getting

Sonic Frontiers was out of business. Are they bacK?