Personally, the 24-70 is a ripper lens and focal range. But the 24-105 may be a better bet for you with regard to overall general use. Both the 17-40 and the 24-105 don't have the IQ of the 24-70, but I feel it may not effect you that much, unless your getting very series with your photography. "William" Ap regular gets great results from his 24-105 as an idea of what it can do, see his posts in Sea - Landscapes.
Get the Lee's in the states, and save the transport costs.
You can always use the 24-70 in portrait mode and stitch several together to get a UWA look. Granted, A bit tricky when shooting seascapes, but that's where PP comes into it's own. LOL