I read 1 review of one of the Sovereign series and while the reviewer found a lot to like, I think especially with the amount of power it could put out, he had several issues with the receiver.
What that says to me is: if you can get a great price, like 50% or more off, it may be a good buy. But when you get up into the high hundreds there are a lot of good models to choose from.
If I can lay my hands on the review, I will tell you what the reviewer disliked. Other than top of the line models (especially from Denon) very very few models come away without something negative. For the Denon 5803 I think all they said was very heavy and large, but everything else thumbs up.
PS I have been using a Kenwood VR6070 for about 7 months and it has proven to be a surprising performer. There are still some around for $400.
I bought the entry VR-5080 because it was below cost, like more than half price off. It's a great deal, and I've been very very happy with my purchase. But later on I look at its specs and the amps are quoted as 80W, 1kHz all channels driven at 6 ohms. I'm like "what the heck" and did not come to expect that from Kenwood's "top" line. While I'm pretty sure the models you've quoted are considerably better, and I think that my receiver is more than adequate and performs very well in my home, it just doesn't leave me a good impression of high quality that you should get with a company's elite lineup.