I would got with the 17 or 17.5". I think I'm just pushing the lower limit of the 19" IP-256 and I am ~178cm tall with ~84cm true inseam (measured in bike shorts, not pant inseam). The bike fits well with a shorter stem (80mm), but I would like some additional stand over height. An 80mm suspension fork or my ~85mm rigid equivalent would make it perfect for my stand over.
For you, it appears that you have longer legs for your height. I would expect you to have a high seat position, but a relatively short reach, though perhaps you have longer arms. I would expect you to have an 80-90mm stem as well.