I'm close to your size (1" shorter and close to same inseam). Assuming that "top tube" means virtual top tube length, then 57.5cm in L sounds good for you. Do you know the virtual top tube lengths in your previous road bikes? If so, then that will help you to decide. Sorry, but can only give feedback on the general size and not the bike (never owned a giant but they look like really good value for $$ bikes).