It's been awhile, and I've owned my HD 800 S's for close to 2 months now.
I moved from the HD 650's to the HD 800 S, and at first I wasn't sure what I thought - they definitely sounded thin (at first) in comparison, and I wasn't 100% confident in my purchase.
However, after giving them a fair chance, and tube rolling (using existing options I had previously already owned, but didn't like as much with my HD 650's) I absolutely love them.
I don't think the Crack + Speedball is the best pairing for these bad boys, but it's whats in the budget for now.
The detail, instrument separation, sound stage, just everything is superb, you can forget you're hearing things from headphones, it just feels like the sounds are going on around you, and when I go back to my HD 650's for a listen - I'm not even sure how I was ever amazed by them - quite interesting how the brain works.
In short, I think I hit a wall with my HD 650's, and the purchase for the HD 800 S's were a straight upgrade and I couldn't be happier.
Looking forward to seeing how they scale with better equipment, looking at the Mainline for my next big purchase!