I recently spent a couple of months searching for the right bike myself, and I would second the idea of spending a good chunk of time test riding. I would also recommend spending the extra money to have a proper fit done from someone who understands your needs and the type of riding you will be doing. It isn't quick or cheap,but once the fit has established the geometry that places you in the most effecient position, you can begin shopping in earnest.

All the top brands are claiming their frames to be "stiff yet compliant" blah, blah, blah. Only the fit can tell you which of these brands geometry makes sense for your body and riding style. There are many bikes that I eliminated this way before finding the perfect match with a Cervelo R3.

Best of luck in your search!