I have the same dimensions that you listed for height and inseam, and I ride a 53 Bianchi Veloce. My top tube length is 52, but the tube is slightly sloped and the effective length is 53.5 (Is your 54 top tube actual or effective?). This length feels good for me, but I would definitely be stretched if I put on aero bars. I would think you might be better off on the 52 also.