The 18-55 is a great all-rounder choice, as is the 18-135 which differs only in weight, reach and weatherproofing. The second lens choice is much harder. I would personally always carry a fast lens so the 23 or the 35 would be my counsel. That said, I was recently in Florence and Pisa with 18-55, 14, 27 and 35 and found that the 18-55 wasn't long enough and the 14 got a lot of use in interiors. There's really no right answer and two is an awkward number. For three, my lightweight kit is 18, 27 and 60, and my low-light set is 23, 35, 56. Ultimately it's your choice, but a nice "problem" to have.