My 5 cents.
I'm 184 with long legs. My wingspan is 184. I would buy a 54. I've geeked out heavily on that (I dont have a specialized dealer near me).
I have a supersix evo hi mod in 56: it's too big.
I have a giant propel L: it's too big.
I have a Cube peloton race 58: it's too big.
Apparently, I never learnt.
On all, I run short stems (80 or so, and would happily run even shorter).
The 168 in 56 would be pretty much the same size as the supersix and the giant: too big.
I do plan to run a c.100mm stem.
Bear in mind the one piece cockpit VB sells flares forward, somehow, so i'd say it's even more advisable to buy smaller than bigger.
Because i dont know how i'll fit exactly, i plan to buy the bar and stem combo, not the fully integrated thing. It's heavier, but gives me more options to dial in my fit. That's a huge thing I feel people forget with those fully integrated cockpits. Unless you know yourself really well, i don't think it's easy at all to size the frame & cockpit correctly.