I tried asking a similar (but not the same) question in 2009. I do not have the answer, but have heard nice things about the Hegel. But I am very happy with the A21. I did get one email from a dealer that the A21 is too much analytical (detailed, airy) compared to the H-20. He said this quality is required for home theater and not 2-channel audio. I was perplexed, since I am looking for more details.
Here is the link to my thread:
Hegel Amplifiers
Here is the link to my thread:
Hegel Amplifiers