Stand over is pretty meaningless. Emonda has a sloping top tube, CAAD does not so CAAD has less stand over. If you were fitting by trying to match the stand over you would get a 48 CAAD which of course would be way too small for you. Eff top tube on 54 Emonda (assuming you have one with the H2 fit) and 54 CAAD are nearly identical. If you look at head tube and stack the 54 CAAD will be a little more aggressive than the Emonda. If you are comfortable on your 54 Emonda, the 54 CAAD is probably right but you might be able to get away with 52 but that would be a very aggressive fit. Obviously visit a LBS and test them