You have received excellent technical advice here from all who have posted. However, I want to add something that I have found in my wandering here in photography. Yes, I have, over the last 5 years, picked up the 10-17 FE, the 12-24, the 16-45 and I do use all of them and enjoy them very much. I have also taken one of the best images I have ever taken of two ships at sea with the 10-17, and it was the only lens that could have done it. Stitching was impossible due to all of the movement within the scene.
Given that little bit as a lead in, you need to ask yourself - why do you want a wide angle lens and how do you expect to use it (not trying to talk you out of it at all). What I have found is that most landscapes are taken at the 24 to 28mm focal length. No real distortion there. As you go wider, you start to pick up distortion, because the lens is having to pull the view from the edges into the frame. In order to accomplish this, the center of the images (the shot that you are actually going after) tends to get pushed back - reduced, so as to accommodate the pulled in edges. Now, as the edges are pulled into the frame, the top and bottom is pulled in also. What this does, is to essentially draw the viewers eye to the foreground of the image. However, you are picking this wide angle lens in order to pull in more of the view - now all of a sudden the close foreground is gaining importance, possibly detracting from the scene you are really after. Sometimes, you do want the interesting foreground to complement the stunning scene - the lake with the reflections of the landscape, etc. That is one of the main reasons why with landscape images, you see something of interest in the foreground - otherwise you would need to crop it down to a long skinny picture.
Because of this, the 24 to 28mm focal length gives you the reach over the foreground and does give you access to the scene that you may be after. Stitching with these lenses gives you the width you may be after. Then again maybe just stitching with the 50 gives you both the reach over the junky foreground and provides a stunning landscape. Other times, its the 85mm, or the 12mm or 20mm, etc.
What it comes down to is the tools in your bag at the time when you are at the location. This is just like real estate - what counts is location, location, location (and opportunity). You need to see what it looks like and what it CAN look like. Then make the appropriate selection and shoot.
What I am trying to say, is just because you have a wide angle lens in your kit, it may not be THE best lens to use for all occasions. This has taken me a while to learn. You may want to shoot the location with all the focal lengths you have and then see what looks best back at the PC. One of the reasons why I am posting is that you have a wonderful kit lens that provides you with an excellent range of focal lengths to use, so that you can test ideas out with and see what works (for you), thus helping you make a good selection for what you need/want. No one can really make the best decision for you other than you. Go out and shoot and experiment, test ideas, and see what the results are.