I have 2 NAD integrated, the C326BEE and the C372. The older 372(7 years or so) is warmer sounding than the 326, yet I wouldn't call the 326 bright. I have Paradigm S6 speakers with forward sounding tweeters that make some amps sound brighter.
I had this struggle that you are having as well. Your speakers with the ribbon tweeter are going to be brighter sounding, and with your preferences you are going to need to compensate for this. Something that helped me is better cables. What kind of speaker cables do you have? If it's just basic stranded copper 10 or 12 gauge, I'd suggest Audioquest Type 4, you can buy it in bulk per foot. It really brought more focus and clarity to the sound, something I was really surprised about.
Rather than trade up components as I did several times, your issue might be easier to fix. The NAD isn't bright, neither is the Onkyo. Just a thought.
I had this struggle that you are having as well. Your speakers with the ribbon tweeter are going to be brighter sounding, and with your preferences you are going to need to compensate for this. Something that helped me is better cables. What kind of speaker cables do you have? If it's just basic stranded copper 10 or 12 gauge, I'd suggest Audioquest Type 4, you can buy it in bulk per foot. It really brought more focus and clarity to the sound, something I was really surprised about.
Rather than trade up components as I did several times, your issue might be easier to fix. The NAD isn't bright, neither is the Onkyo. Just a thought.