I think you are overthinking this a bit. With the riding you will be doing, weight should not be a major concern for you. Of course you do not want some 30lb tank under you but, I think that, in the grand scheme of bike buying for guys like us, ie: recreational cyclists, most modern road bikes weigh much less than when I started back in the '70s. Back when I began riding, a 20lb bike was considered super lightweight. Now, even bikes like the aluminum Synapse come in at about 21lbs or so for my size (58cm). What is more important is fit and frame design. A well designed, proper fitting, aluminum frame will be a far nicer ride than a lighter carbon frame that doesn not fit your riding style. To some, carbon is the be all and end all in determining bike quality. i like to call those people "wrong." Frame geometry also is very important, I have a Synapse and for me the ride is very comfortable, but it will surely "get up and go" when stomped on. I do not see the sluggishness that some have reported. My only foreseeable upgrades are the wheels and the saddle. Other than that I do not see myself wanting a "better" bike for a long time to come...well maybe wanting but nt needing.

I also would not worry too much about componentry if your bike comes with 105. I have been riding 105 since 2005 and I have never had a singlt issue with it....not one. I knew a few racers when i lived in New Jersey who raced on the stuff and loved it. It will last you a good long while and do whatever you need it to do and do it very well.