Bruce ...
Here's the conclusion I've garnered from a realiable source:
The Ref-6 challenges the REF-10 in some important areas. While the soundstage width and depth aren't quite as good as the Ref-10, the REF-6 has the advantage in musicality, tonality, and overall realism. From the first note, it is clearly better than the REF-5-SE and in another league altogether. It gets digital really close to analogue and is quite amazing in that area. From what I hear, the REF-6 is one of the finest pieces ARC has produced to date ... at less than half the price of the REF-10. Its on my bucket list for sure. Hey, anyone want to by my trusty REF-3?