I have a Ref 110 and use a 20 amp Shunyata Black Mamba HC. I also use Shunyata power cords on my ARC LS25 mk2 and Ref 7. I am very happy with the results.
Music Direct was and I think still is having a big sale on Shunyata power cords. I bought my Black Mamba HC as a demo from them a couple years ago.