I want to make points in my very limited humble opinion:
1. To the OP, as someone else seemed to say above, I wouldn't fret this too much. You bought a quality piece of equipment. I wonder if the differences between the ARC and Primaluna will be marginal. We cannot forget to enjoy the music. I'd ask myself, can I live with what I bought? And the good news is you can always buy a Primaluna and sell the ARC--or keep the ARC. I bet it's amazing.
2. On Kevin Deal being a used car salesman. I own a Primaluna HP Integrated. And, I have had some a need for customer service for two issues. Kevin Deal was simply amazing. He called me on nights and weekends. He followed up immediately each time. His staff gave him my detailed messages. He understood the messages BEFORE we talked. He told me, "Dude, I will not leave you hanging here." Yes, that language is casual and so Southern California--I'm in Chicago. But it was cool because his casual language meant something more than formal language from other dealers--he stood by his product and was awesome in the process.
I bought an open box item. When I had an issue with the remote and mute function on the amp, Kevin worked through it. When we couldn't get it easily resolved, Kevin shipped me a brand new unit by Fedex 2 day from Cali to Chicago. He told me not to ship back the original product until I had the replacement up and running. He said you don't want to be without a stereo during this process.
I was so happy and blown away (because of the service and how great the amp sounded) I offered to pay full price for the new unit, as Kevin had only really offered to sell me an open box one at a discount. Kevin's response to my offer--"Just enjoy the amp man."
I don't think Kevin would be as successful as he is if he were a used car salesman. Kevin needs me to keep coming back to him. Have we all seen his facility and stock? He can't keep that facility up by selling snake oil or BS. Customers are fickle and discriminating. If Kevin sold me a tube and told me it was better than another tube--yet it was salesy garbage/puffery--he would either need to fool me with bias and BS or I can independently find him to be wrong.
I don't want to come off like Kevin is the second coming of our savior. I just want to say that he is a class act businessman. I buy from him because of his service and fair dealing.
By the way...I do own a Primaluna HP integrated, Manley Chinook, a host of tubes and DH Labs cables, which I bought from Upscale. I am not related to Kevin in any way and have never met the man in person.