I currently have an XSi with the following lenses:
I'm happy with the nifty and the 55-250 but I don't love the 18-55. I'm looking for something that can provide better color and contrast to my photos, not to mention better AF and sharpness. Honestly, the direction I'd like to move in is sticking to prime lenses -- I don't care all that much for zooms on the wide end. I've walked around with my kit set to 24mm, 28mm, and 35mm at different times and I rarely felt the need to be any wider, so I don't think I'd miss the <24mm range very much.
I'm looking for something that I will be using for landscape shots for an upcoming Yellowstone trip as well as my primary walk-around lens. I know the Sigma 30 is highly regarded but I'd like, if possible, to stick to a Canon EF lens. I know there is a 24mm 2.8, 28mm 1.8, and I believe a 35mm 2 available. What might you suggest for these purposes that will provide me with better color quality and sharpness than I am getting with the kit lens at those respective focal lengths?