I've been listening to the H6 for the last few hours, it is a unit with a lot of hours on it. I'm using it with a Stoner Acoustics UD100 DAC and a JDSLabs C5.
I do not think this H6 has a V shaped curve as the mids are very well present. Overall I find the the focus to be on the bass and the mids, treble isn't too forward or bright or sharp at all. Bass body and punch is very good, the mids are rather warm and very smooth, I can not call this headphone neutral. It is a more centric sounding unit.
Soundstage is pretty good, nothing exceptional and I find the overall sound can be compared to the Momentum, but the Senn sound was even more relaxed and less centric.
It's better as I expected it to be but I find the price too high for what you get sound wise, there are other and cheaper options. or even slightly more expensive options that give you a lot more.