The only way to determine which one is better for you is to go and demo them yourself. You will find that in these forums people are pretty biased as far as their favorites go. So, you could get 10 people liking the HK, 8 people prefering the Sony, and another 5 suggesting you get a Denon. Just remember that no matter how many people respond to a particular thread in favor of one over the other it really doesn't tell you all that much, because you are asking for THEIR preferences, which probably has little to do with your own preferences. JMO. Good luck.
The one thing I will offer is that I know the HK AVR8000 is a very large receiver. Deeper than most. Some people have problems placing it because of this.
Mark, I see you edited your post.... The Harman Kardon AVR-8000 is NOT avaialable yet. NO ONE KNOWS YET. I answered another thread regarding this same question two days ago by the same person. Lol... When the AVR 8000 BECOMES AVAILABLE , i'm sure many will comment on the pros & cons of this receiver.. it looks promising too say the least. As far as the STR-V555ES, it's last years model Sony ES. Now, i owned (briefly) the STR-V444ES which is the same as the 555ES with the exception of the remote included. I can tell you i didn't like it. It was ok in HT but pretty bad in stereo IMO.