I would check these out in a store from a friend or by renting them:
Tokina 11-16 2.8
Canon 17-55 2.8 , 10-22, 15-85,
Tokina 16-28 2.8
I used to have the 16-28. Never had a prob with its sharpness or speed. That can be used on FF later... and the approx 26mm isn't that bad.
16-28 is good. I'll only warn you that it can't use filters (though there are special/expensive way of doing it). Filters are very important for landscape photography.