I really like the Audio Research Ref line. I am planning to upgrade my preamp to a Ref 5 maybe next year. The VT100 I had used a regular 15 amp cord but the Ref 110 uses a 20 amp. So when I bought my Ref 110, I tried a bunch of power cords from a couple dealers I frequent. I like the Shunyata power cords the best of everything I tried.
The other thing that impressed me was that Audio Research used Shunyata cables at shows. I am sure that they tried everything available to see what sounded best with their equipment. The fact that they chose Shunyata just helped confirmed my opinion.