Going to Italy

Wow, those are some nice shots.

To the OP, I agree with the 17-55mm. I travel to San Mauro Pascoli at least 7 times a year, it's where the factory I use for my accessories collection is. Anyway one of my close friends brings his 17-55mm along whenever he flies over with me. It's imbedded in my brain how much he loves this lens, and the fotos are very good, thus why I went dslr -- I was jealous.

Besides that you're going to love Italy, all the cities you named are very nice. Have fun, and happy snapping.

17-50 was, as expected, on the camera most of the time.

10-20 got pulled out a LOT.

70-200 got a few uses, as did the 2x. I couldn't fit the 70-200, 10-20, and camera with 17-50 in my Kata T212 so there were a few times I wished I had the 70-200 and didn't, but very few. I'm eyeing that downsized Sigma (50-150?) now though... Having the bag in front was awesome. 12-14 hours a day with it wasn't so much. I was able to wear it through a lot of the museums that disallow bags, so I'm thrilled with it, despite its shortcomings (size).

Transferring snapshots now - I pretty much filled up 5 2GB cards, so I have a bit of work ahead of me.

I had one run-in with some gypsies, my own fault - I missed the sign saying "out of order" on a ticket machine (for the train) and the 2euro was visible but stuck - the only thing I had to pull it out was a rolled up 20euro note and I figured that was a bad idea... Even at 10euro (vs the 8 it shoulda been without the lost coin) the 2 24hour passes paid for themselves...

I did not end up taking the Pelican case - needed that extra bit of space I lost having no other carry-on. Carry-on with the camera was fine though.

C

Whatever you take, make sure you also bring back! All it takes is putting down your bag for a few minutes and it's gone. Watch for pickpockets and be vigilant around many tourists. The thieves blend in with the people and tourists. I lived in Italy for over 3 years, so I know.
Another thing; Yes, streets are narrow in some Italian cities, but in large cities like Rome, it's not true, so bring a wide angle lens and in many historical places they don't allow the use of flash, so make sure you have a fast prime for those low light, no flash situations.
These is the best advise I can give you! Enjoy your trip...