What do you want from a road bike? Pure thoroughbred race geometry or something with slightly raised bars (ie no spacers for most of us)? If your budget is 2K, it’s hard to see past the Giant Defy Advanced – bike of the year for 2013. Buy the best frame you can afford. Even relatively cheap groupsets like Tiagra shift as well as Ultegra 6600 these days. More money buys less weight and that’s about it. Big brands have more buying power from Shimano, so can push prices down. Smaller companies such as Ribble then follow by sourcing frames as best they can to compete.
For the budget, there are no bad choices, just decide what suits your needs best. And be honest about the riding you’ll do.
Disclaimer: I have a Giant Defy Advanced SL (and a TCR). And it is a fantastic do it all bike, race, club rides, commute – well in the dry, anyway!