My Advice...
Good Triple butted Alu frames can be as comfortable and stiff to ride as a cheap carbon, sometimes better. CAAD's are some of the best Alu frames you can get.
105 is a great groupset. Quality without breaking the bank.
If the wheels are cheap may as well get them, saves you feeling the need to upgrade at more expense down the track.
Never buy a bike you can't ride first.