In the same general line up would be the defy 1 (I shopped that price range, your up two notches), the Felt z85, the Fuji Sportif, cannondale synapse.
The defy 0 may have better wheels than the defy 1, not sure there but for just starting out Ultegra may not offer you loads of improvement over 105. The Fuji gran fondo in some level may be in your price range too. Pounds to dollars not working mentally for me. I would not smoke your whole budget on the bike, leave some for clothing and stuff like spare tubes or a nice cycle computer :-).