What are your opinions of Sim Audio amplifiers?

I have the 600i integrated and the 430HA headphone amp.  Both pieces are keepers.  The 600i is mated to Harbeth P3ESR SE speakers and it rivals my main system for enjoyment and sound quality.

Keepers, unless I decide to try out a high end tube headphone amp.  Hah!

Thanks, Simaudio for the forum clarification. Always good to see a manufacturer here. 

Agreed. Thanks for weighing in Costa.
Personally, I have found Simaudio’s level of customer service exemplary and enjoy their components immensely. I have owned the 780d DAC, the 740p and 850p preamps and the 870a stereo amp and 860a v2 monos. I believe their performance has been commensurate with their price all things being relative. That said, I was also quite impressed at the improvement of the 860a v2 in stereo over the 870a. And the retail on the 870a used to be $22k and now the 860a v2 is $18k. Not sure how many manufacturers end up pricing improved products lower. In addition they offer 10 year warranty on their products. Which seems incredibly rare.

What is the main SQ difference between 860v2 and 870A ?