If you're staying with a crop sensor, and you like landscapes, nothing can beat the Canon 10-22mm. It's simply fantastic in both build and optical quality.


I wouldn't be too worried about the aperture being a little higher as with landscapes you generally want a deep depth of field anyway so you'll find yourself stopping down to narrower apertures.


Don't discount the Sigma 10-20mm either. I have a friend who uses it (on a Nikon D80) and he's taken some beautiful photos with it.


Hope this helps. Ben