I used to own Audio Research Ref 160S Amp, Ref 6SE Preamp, and Ref 3SE Phono. I replaced these components with the CH Precision M1.1, L1, and P1. I now have the CH Precision M10, L10, and P10. I had a chance to listen to an all Nagra system at my local dealer with the same speakers that I owned at that time (Vivid Audio).
First, comparing CH Precision to Audio Research, I much prefer CH Precision, for the same reasons that others have reported with respect to CH Precision generally. The speed, dynamic range, power, and harmonics are far superior, in my opinion. With Audio Research (and with other systems that I have owned), I found that I was limiting my listening to a narrower type of music - mostly acoustic music, female vocals, small jazz ensembles, and chamber music. The electronics could not handle rock, orchestra, or other music with higher current demands. CH Precision gives me a far greater sense of natural, live realism for more types of music. There is nothing about the positives of Audio Research (and, as you know, there are many) that I miss.
Second, comparing CH Precision to Nagra, I found the Nagra to be a little lifeless when compared to CH Precision. Nagra did not give me the soundstage, inner detail, quickness , and realism of CH Precision.
Of course, all of this is system and room dependent. And, your tastes may be different than mine. If you get 10 opinions you may get 10 different answers.
Good luck. And, if you are looking for a referral to a quality dealer who has available factory recertified 1 Series CH Precision (from the many trade ins of the 1 series to the 10 series) or new 1 or 10 Series equipment, feel free to message me offline.
Nathan