@j-wall
Primaluna gets the big stuff right. The overall tonal balance, level of detail and bass. ARC goes beyond this. It gets the sound fully fleshed out and refines all aspects. Details like cymbals become unmistakable brass instead of just sounding like the treble of cymbals. Voices take on the full lush nuances of the real artists. Bells completely change with ARC, being rendered stunningly realistically… the richness and depth can be startling. Bass notes and sounds are more multi varied and differentiated… less single thump. The background… noice floor lowers… a big deal… allowing you to fall deeper into the music. While PrimaLuna is musical… ARC takes it to a much more compelling level of emotional connection.
ARC produces fine scientific like instruments letting you discover nuances you never knew existed in the music. Over time, I continually learn more and more about how good they are.
ARC has a company sound that has been refined generation after generation with a goal of musical reproduction. As @richopp points out, they occasionally made a misstep, but overall they have marched relentlessly towards reproducing the full experience of music. The newer and most costly succeed to the greatest extent… but buying as high up the ladder. But any of them will buy you into the experience.
My audio guy gave me a book, “Making the Music Glow”, by Ken Kessler on the history of Audio Research after I bought my final piece of ARC Reference gear. It tells the story of a vision of music from it’s origin. Reading the book, I really got it. It was never about money… it was about a vision to create an believable musical experience in the home.
An ARC preamp will work great with your amp. No question. You will get an upgrade. But it will likely make you wonder what would happen if you switch to a good ARC amp. And that will get an enormous upgrade. The combination is incredible. Over f the decades, nearly by accident I ended up with all ARC gear… the synergy is incredible. For a chang I can’t conceive of changing… well maybe just upgrading as new models become available.