With that budget (and less) you can get a great road bike.

The setting you're talking about (alu + carbon) with Ultegra is great. You could do very well with 105 as well, and invest more in the accessories: great saddle, great bike shorts, good rigid cycling shoes (they make a world of difference on climbs, and you'll have lots of those in Italy) with automatic pedals, etc. Wheels also matter, but it's not my forte.

At your weight, the lighter bike will make a huge difference.

A good saddle and a good fit will also allow you to be much stronger. When you can't sit right on that bike, you can't really transfer the weight to the pedal.

Good luck! And get back to us with your shopping reports! Welcome to the wonderful world of TE.