Having just read your other thread about either the 6D or the D750, Why not look at the 5D3 from Panamoz, it isn't much more than the ex demo and it's a new camera. My reasoning is on your other post you mentioned that you had tried the Nikon and struggled with the menus, whilst you may get used to them, it is a risk and for me a very expensive risk. You also commented that ultimately you would like the 5D3.
It has a superior focus system to the 6D although the 6D is supposed to be marginally better in low light (by about 1 stop). I know which way I went