???What's The LEAST Expensive "End Game"Amplifier You've Ever Heard???

If you can get your hands on one of the 100 limited-production VPI 2990D Integrated Amps, go for it!!!
A full Tube Integrated Amplifier that really sings. They came up for sale less often than before and they will be everywhere between $2,400 and $3,200. It is built in the USA with mostly USA-made parts and has a very decent flexibility for rolling different tubes which can really tweak the sound of your music.
This may be true of all Tube Amps, but speaking for this one, it will be your endgame Integrated Amp with tube rolling (sound tweak) options!
The only caveat I have is that the MM Phono Preamp seems to be solid state, and although it has really great sound some unites have a subtle hum that can get in the middle of the listening experience... Nothing that would deter me from buying it again.
Good luck with the search and, please report back on your decision and experience with it.

I have been very pleased with Accuphase and consider it to be my ed game SS Preamp and Class A amp. The integrated are also excellent. I would look at something which fits your budget, definitely used, these are built like tanks.

Audio Research Reference 160.

On the Integrated side I would have to say my Ayon Triton. It’s fully tubed on the pre and amp side. I think the retail when it was new was around 10k, however I purchased it used for around 3k 2 years ago. 
 

It has so much detail and clarity I could not imagine replacing it. Plus it’s the sexiest looking amp ever! 

Coda S5.5