I'm currently riding a full carbon BMC with Sram red 10 speed and mavic cosmics for about 500 quid. Bargain huntings my thing, I'm not gonna spunk over a grand on an off the peg tiagra bike.
Caad12 framesets now just over 400 from last year so might go that route.
Buy the full bike. Knowing cannondale's frame only pricing strategy it will be a much better deal.