I post this regularly in road disc threads, but just be aware that frames like the CAAD12 might be getting discounted for a reason – if they’re built with old standards (Q/R, post mount brakes) which are just about to become obsolete. Everyone is ditching Q/Rs for bolt-through; I’ve recently bought a brand-new-for 2017 Giant Contend Disc with Q/Rs and I understand for 2018 all Giants will be bolt-through. Shimano now only seem to offer flat mount brakes. I considered buying an Enigma Evoke Disc frame bundle ‘cheap’, but I sacked that when I went shopping online for a hydro groupset to fit it, NO ONE was selling a complete Shimano disc groupset with post-mount hydros. And flat mounts are not reverse-compatible.
It looks like they use a post-mount fork (taken off the older CAAD10) and a flat mount rear
http://road.cc/content/review/182996-cannondale-caad12-disc-dura-ace
whereas in that cyclingtips comparison, the Supersix disc uses a bolt-through fork with a flat mount caliper.