I have the auditors and listened to the 805 signature's. I still have not finished the room they are going in, or bought the electronics.
Here is my input:
The signature 805 was a great speaker, it imaged very well, and had a good balance, a little exagerated in the high frequencies.
The Auditor had more detail, more air, I felt it did not exagerate any fequencies. And I honestly feel it made more bass.
I listened to Diana Krall's Live from Paris CD. And on track 11 "A Case of You" I heard a almost wet sound in her voice in between words she was singing. The only other speakers I heard that same "wet" sound on were Wilson Benesch Arc's and a pair of Dynaudio Special 25(I could not afford them)
I listened to Might Sam Mcclain's "Give it up to Love" track five, the sound stage on the Auditor was bigger than on the 805. And in the beginning there is a piano playing and I was simply amazed by.
In the end both are great speaker's but I felt the Auditor was more suited for what I wanted to hear. That being said I really do not listen to much rock music so I did not play a single piece of rock when I demo'd any of the speakers, I have a felling that the 805's would probably do a better job with rock due to it's metal tweeter.