High end stereo preamps? Worth it?

Yes.

it depends on the room but if you’re good with the room, then yes for sure.

i went from Rotel preamp to rogue to Cary 98 then Cary 05 then arc 5se then finally audio research reference 40th anniversary.

the arc 40 is the best preamp I’ve ever owned and it’s hands down one of the best moves I’ve made.

How about the Benchmark (LA4)?   I didn’t see it on anyone’s list above, but I have heard a few good things about it personally. Just asking for opinions, I have no horse in this race.
— Jim

Parasound Halo JC2BP provides a sublime preparation of the signal at $4,500.

In my experience, a good preamp took my system to the next level (adding EAR 868L to Pass xa30.8). The vibrancy that it brought to the music the first time I turned it on I won’t soon forget.  I had been running DAC direct but correctly realized something was missing.