OP,

I've just glanced at the geo. chart for the Norco (Valence A4) you are considering. You do need to check fit in person, but ... based on the information you gave early on in this thread, I would guess you would need the 51 (not 54) in that frame.
That "51" is pretty much dead-on equivalent to most "54"s with compact geometry ('endurance', not 'race'); examples would be Giant Defy Medium or Spec. Roubaix/Secteur. The Norco "54" would be a "56" or Medium/Large in those frames.
By the way, that size would do away with any concerns with standover you might have.