Campag is right. 50x11 at 28.5 MPH at 80 RPM. (43 MPH at 120 RPM) To maintain that 28.5 MPH pace, in the drops, on flat land with no wind for a 155 lb rider and 20 lb bike, they'd have to output >400W. That's roughly 6 W/kg. That puts them in the Cat 1-2 - World Class on this chart. So unless you're constantly riding down massive straight grades, anything higher is unnecessary. Even then, your gearing is better spent where you'll be riding the majority of the time, not when you're flying down a hill.