Is the D40x limiting you in any way?
Out of the two options, I would go for the Tamron 17-50 f/2.8, because I think the ability to have f/2.8 would be more important when traveling, and when you need longer, you said you have a 105VR.
Not really. Only indoors with low light. But I can take just as good photos with the D40x than with the D90.
As for the 105VR, I don't think I'm taking it, it's huge and weights a lot. I'm sure I'll miss it, but carrying it around wouldn't be nice.
Some of the older Tamron models won't autofocus on your D40x, as internal motors were added fairly recently, so shop carefully.
I would go with a superzoom over an f/2.8 lens for travel (and I have), just for its ability to work in a much wider variety of shooting situations while allowing you to pack light and not worry about switching lenses. I don't see why you would really need the larger aperture while traveling, unless you're planning to take a crapload of street candids with less-than-decent ambient light.
I'd recommend an 18-200mm VR. I don't see why you'd need a D90.
This Tamron is new, but I'll give it a second check to see if it has a built-in motor.
As for the 18-200, I guess it's a dream traveling lens, but I'm also thinking about the future and my normal use when home. Since having the 105VR f/2.8, I can't but think of my next lens being also f/2.8. But they are so expensive.
In today's Economy - I say just buy a used lens that would suit your travel needs... save your money for Europe...
I'd be surprised if you got that much for your D40x - seeing that the D3000 kit is available for $399 refurbished...
Ohh...you sound just like my mother.
I know saving the money for Europe would give me a better chance to go and visit more places, but the truth is that I enjoy photography too much to go there and miss having a better lens with me.
As for the D40x selling value, I guess the advantage of living outside the US is that just as photo gear is more expensive when new, you can sell used equipment for more. And since I bought my D40x in the US, and I would buy the D90 there as well, I think I can get a sweet deal from the D40x.
Hey HarryPot, I was debating a similar thing in another
thread. I ended up purchasing a lens rather than a body. There is some good discussion there that may help you make a decision!
So you're buying the 35 f/1.8?
I also see this lens as a great alternative, and one in which my wallet won't suffer much. It would be great for museums and places where no flash is allowed.