Travel lenses -"less is more"

I am trying to find the minimum number of lenses , ideally 2, that I can use while traveling in Europe. I have a D90 and the following lenses:
18-200, 12-24 Tokina, 17-55/2.8, 35mm, 50mm, 90 Macro Tokina, 300mm.
Interested in architecture, landscaping, people in the streets

I used to carry just the 18-200 but I am not satisfied anymore with the quality of the pictures taken. On the other hand the 17-55/2.8 doesn't cover enough. Using several primes is also too frustrating when I am on he run.

Can I use a good, possibly light combination of one of my existing lenses with a 2-nd lens only? What should I buy? Anything but the 18-200 Thank you.