I placed a pre-order for one this morning. Still kind of on the fence about it with the conversion cost and long wait, hoping I don't get buyers remorse, but whatever... All aboard the hype train!
Seems like it will be an interesting reference amp from what I've read, and should contrast nicely with the Darkvoice in my main chain.
In regards to your initial question, I guess it just depends what sound you're after. It's a neutral amp, any colouring will be done by the source and cans you're listening with. Considering the transparency and low output impedance of the 789, I think it's likely to pair well with the LCD's, but have read that some find the HD800S a bit too bright with it. So, you might want something on the warmer side for them, but ymmv. Also, the signal path isn't truly balanced in a few sections, so I doubt using just SE will be much different if you were thinking of getting one for going balanced.