3rd Cannondale CAAD 9 if your buying new. If your going 2nd hand then its hard to beat the bargain setup i've accumulated over the years, I've a 2004 CAAD4 (new to me in Dec 2005 having covered very few miles) and cant fault it apart from not being the lightest choice. People dont believe me when I say it only cost me £300, especialy people riding bikes the spend 10x that on at sportives! Since then I've bought Shimano r-550 wheels, a 10speed dura ace groupset, bontranger carbon bars, and FSA SL-K cranks to shed some weight.
Still on the upgrade list;
Carbon seatpost (currently OEM alloy)
Saddle (currently OEM, but suprisingly comfortable)
Stem (currently OEM)
Wheels (again)
Pedals (bargain basement early 00's look pedals at the moment)
Will be well under a grand and I'll have had 5 years use out of it while I upgraded it! At soem point I'll upgrade the frame, but I'm bot in a hurry, na it will probably be a 2nd hand CAAD9.