1) your best bet is to go into your local bike shop and see what they have to offer. This will allow you find the correct size bike you will need.
2) Im sure I will get flamed for this...but in that price range you are looking at an aluminium frame w/ hopefully a carbon fork. Most alum frames will provide a nearly identical ride so dont get hung up on brandname or particular alloy blend.
3) the majority of off the rack bikes will come with shimano. In order lowest to highest, sora, tiagra, 105, ultegra, dura ace. 105 will perform great, its just a little heavier than the next 2.
4) carbon seatposts do little to nothing towards dampening the vibration, same for carbon stems and bars. dont be swayed by that.
5) The wheels provide the biggest difference in ride quality.
6) aero trumps weight savings.

dont forget about www.Bikesdirect.com so long as you can assemble and maintain your ride yourself, if you cant then buy from the lbs that seems to have the best customer service.