I need help deciding which wide angle lens to get. I love the idea of the Canon 10-22mm, but it's an EF-S lens and I want to eventually upgrade to a full frame sensor so it won't work for the long haul. I already have the 24-70m f/2.8L so anything from 20mm up seems too close to what I already have. I would love to get the 14mm f/2.8L, but don't have the $2000 to drop. Looking to spend up to about $1000. Maybe the 17-40mm f/4L (but I just don't know about being limited to f/4). Thoughts????