Yes, I have tried all the permutations of Audyssey, HDMI, etc. One of the problems with the 605 is that the Audyssey correction is not available with the HD codecs, due to processor limitations, I guess. And it is Audyssey 2EQ, a limited version, which does no subwoofer equalization.
Regardless, the analog output on the 550 blew away the HDMI on the 605, in terms of harshness, detail, and musicality, especially with music. The 605 sounded thin and tinny.
I guess my main question is what receiver will equal the performance from my 550. Just a small step up, like to the 8xx series? And finally, what receiver will equal the analog performance from an Oppo 83 (SE or not)?