At 133 the head tube is plenty aggressive if you're getting a small. Actually looking at the geometry compared to my Noah a small would probably fit you well. The difference between it and a CAAD9, other than the frame breaking, is that the Ridley will steer a touch slower but be a bit more stable. If you go down to a 50 in the CAAD the frames are very very close in geometry, while the Cannondale has a shorter head tube often the type of headset changes this number.

Unless you're slammed onto your headset now and need to get lower, the headtube would be a non issue.

I'd consider the groupo, if you prefer the SRAM over Shimano or vice verse that might be the swing vote.