everyone has different bodies, but I am pretty much your height and am very comfortable on a 54 with a 545 ett, but for me is very comfortable with a 90mm stem and bars that have relatively short reach.
I have ridden this bike for nearly five seasons and from this experience, I feel it is better to go slightly smaller than too big. This works for my body, may not for you but it sounds like we have a similar body shape.
Thanks for the quick reply. Yup, its what i am thinking, the 420 wide bars and shorter 100mm stem seem more appropriate for me, perhaps I would prefer to 175 cranks, but that should matter that much. BTW, do you mean 554 ETT, or do the older models have a 545 ETT?