Well, for starters, there is no such thing as a bike that will climb hills with little or no help from you. Unless it has a motor.

You should try riding the bikes you're interested in, and try different levels of the same bike, so you can get a feel for which frame fits/feels best to you and whether more expensive components seem to be worth the extra money. I think you will find a bigger difference going from Sora to 105 than from 105 to Ultegra.

FWIW, I upgraded from an aluminum Trek 2000 to a Madone 4.7 last year, and I am not much faster now. I am way more comfortable, however, which was my primary reason for upgrading.