The other point about 7.1 for me is how significant the difference will be for 7.1 with the 861 v4 and 7.1 with the 861 v6. I realize that the v4 is only simulating the extra discrete channels but when I had my system set up that way, it sounded convincing.

861v6, DSP3100 x3, D1500, Revivers, DSP33 x 5