Upload & Sell: Off
We're just shooting the breeze, right? Here's my thoughts:
1. based on the choices you give, I'm assuming that you're staying with DX (or at least, your D200) for now.
2. The 17-55 would be your "pro zoom", and it could potentially replace your 18-70, 35, and 50 (not saying you should toss them, but this lens would be the new king of your D200). I myself like Sigma lenses, so the 17-50 would tempt me here, depending on your budget...
3. ... because it would give you more funds, for instance, if you also wanted to add a 70-200 f/4 or one of the f/2.8's for "sports", which is a little vague. Some sports would be fine with an 85mm, some require 300mm or more.
How much do you use your 35mm, 50mm, or 35-70mm on your 18-70? I'd use this to decide between the 17-55/17-50 vs the 18-35.
Just my thoughts.