This was asked about a week or so ago http://www.bikeforums.net/showthread...ram-durability

You say double tap vs STI isn't important; would try some bikes out with the different systems, as they will give a very different feel to how the bike shifts.

For weight, having light weight wheels will make more of a difference than the groupset, and there is little point in getting a bike which weighs less than 6.8kg. It's doable, although probably not for your budget, but as it's below the minimum UCI allowable, it's pointless.