I have heard the Abyss and I don't understand the hype. Not a fan.
The fit is pretty crazy, it just sits on my head, I was pretty concerned that it was just going to slip off my head. They are kind of speakers over your ears.
The HD558 is somewhat warm. The 800 is not. If you think the XPT100 is very tinny and fake sounding in tone, you will likely come to the same conclusion as the HD800 given the model you have is the same as the HM5.
But you find your cheap speakers to sound realistic ? Obviously speakers sound more realistic compared to headphones, but at a price, a large one. I don't think any $3K speaker setup will beat a $3K HD800 setup, but others will argue otherwise.