I totally agree with Richard. The signature 805 is leaps and bounds better the than 805. People that say it is only a finish upgrade don't know about the B&W line, because that is not true. For starters, all you to have to do is look at the binding posts. Where the N805 uses copper, the S805 uses silver.
Anyway, I've been using Musical fidelity with both the N805 and the S805. They go great together. I would suspect that even the N805 would be better than the Audience 52, although, I have not heard it with Musical Fidelity gear.