At this price level you have a lot of very good options. Gryphon, Accuphase, Vitus, Boulder, Pass, T+A, Manley, Line Magnetic, BAT, just to name a few.
Given youre talking ‘end game’, the most important thing (in my opinion) for long term satisfaction is to concentrate on the emotional response you get from listening to a particular amp, as part of your system as a whole. Try to ignore price and measured performance (and reviewer descriptions) as these do not correlate with your own personal enjoyment of a piece of gear. If you really want this to be your last amp purchase, then I think you are more likely to be able to step off the upgrade merry-go-round if you demo widely with different topologies (tubes, SS, Class A, A/B, D, hybrid) and ultimately follow your gut (heart) rather than your ear. By this I mean pay attention to how you feel when you’re listening, rather than the level of detail being excavated from a recording, or size of soundstage being drawn.
Good luck and enjoy the journey.