In my case, Audyssey is top notch in terms of soundstage, but that's me.
I'd even say that it's a real case of "love it, or hate it" though.
If you seach into this forum, you'll find lots of useful info about Audyssey.
Regarding to the Denon 4806CI, "I believe" that it's equipped with the HDMI version 1.2a (altough their tech. specs says it's 1.1 compatible... useless info, as basically most of their tech. literature). The least case would be, IMO, version 1.2 though.
Cheers.