Audio Research LS-15...time to upgrade or just keep retubing

I own the LS-15 that is now almost 25 years old.  About 10 years ago I sent it to Great Northern Sound and had it modified/upgraded.  It was a fairly major overhaul that cost me almost $2000.  The LS15 has always been trouble free (before and since the upgrade)...and I have been happy with the sound.  However, I am due for a tube replacement and am debating between continuing on with the LS-15 with new tubes OR considering that it may be worthwhile to consider upgrading to a newer/better line stage.  Although I am not stuck on the Audio Research models...that would probably be my preference based upon my experience with the LS-15.  I know the LS-15 was a solid performer in the Audio Research line but a couple of steps down from their better models.  I think the GNS upgrade mod probably raised the level of performance of this unit pretty significantly...but that was 10 years ago.  Just curious to hear some input from others who might have had experience with some of the newer ARC line stages vs the LS-15...and/or experience with the GNS mods relative to stock ARC models.
Been a long time since I’ve listened to a LS15 but in its day it was a really nice preamp. Not sure what a GNS goes for on the used market but a stock one $13-1500, so maybe the GNS $2,000? Hard to believe it’s been 25 years!

The latest ARC preamp I’ve had in my system was a LS25 MK II and my former ModWright SWL 9.0 SE was better... I felt much better. Between the two preamps the LS25 seemed cold and boring compared to the 9.0. The LS25 is no slouch but when I put it up against the 9.0 I was surprised to say the least.

My guess is you’re going to have to find something used for $3K to be a significant improvement over your LS15. I personally wouldn’t spend anymore on you LS15 on modifications, especially if you’re looking at another $1-2K. For the cost of a major upgrade and what you can probably get out of your LS15 I bet you can find better such as a Ref 3 or a MW LS36.5. The new ModWright SWL 9.0 AE or LS100 are other preamps worth reading up on as well if you’re looking for new and wanting to spend less. Lots of options out there that’s for sure.

If you’re tired of tubes, there’s Ayre and Pass, among others.