Hiya,

Here's what I'd do. I'd buy the 17-40 like you mentioned and also pick up one of Canon's 50mm prime lenses (probably the f/1.8 one). You'll find the pairing of those two great for travel. With the 50mm being so small and light and the 17-40 giving you the wide angle you seek. The 50mm also plugs the gap between the ranges you mentioned but honestly it's not that big of a deal to have a gap like that.

These two are well within your price range.

The 17-40 is a heavy beast....I hope you're already aware of that!