My main problem with the BH is really just price, but also because I just don't know if I want to deal with the fact that tube products are high maintenance--you have to continually put money into tube replacement, and you have to warm them up for a long time before you listen, and they are also much more fragile. I also have to wonder just how much better it sounds when it costs more than twice as much. 10% better? While I understand at this level of the game, diminishing returns is the worst thing, but still, it's a bit hard to swallow. I suppose I have to hear a BH with an O2mk2 in person to see for myself. I mean, when I heard the O2mk2 with the 717, it convinced me that spending thousands of dollars for a flagship electrostat rig was worth the money compared to how much more enjoyment I got out of the listening session compared to any dynamic headphones I have ever heard--including many of the most respected ones.
I can understand that. That's why I'm building my own. It allows me to pay as I go, so to say. The tubes are a pain, but at that level I am willing to do the extra work. I wish I could tell you how it stacks up against the KGSSHV, but it looks like there's still quite a bit of planning involved with that project.
I would say the KGTT vs the BH was about 7-10% but it hit that perfect spot for me. Much like how the 717 and the O2 convinced you to buy an electrostat rig, that combo made me realize that since I have a flagship electrostat headphone, I want to be able to run it to its full potential. For me, the O2 are my end game, but that doesn't mean I'm not gonna go back and explore low-fi to high-fi and everything inbetween. Oh and I forgot to mention that I'm glad you made your comparison of the LCD-2 to the O2. I'm planning to pick up a pair of LCD-2 sometime in the future as well, but I was curious which rig to build up first, so your impression made me feel vindicated in my decision to go O2 first.
But the real jump up is TT to SS and the TT is better than the Stax offerings. My opinion on the power output of the KGSS v KGBH is that the KGSS is already capable of destroying my ears, more isn't what the KGBH brings to the table that should be focused on. Its better and louder but the better part is the reason you move way up in price. For me its deep into diminishing returns and I have no complaints about the KGSS, though a smaller tighter case would have been nice. No bringing up that I could have gotten the DX 
