There is no L lens that's particularly wide on your crop sensor camera. Aside from a fisheye with strong distortions, the widest L prime available is the $2000+ 14/2.8L II and that's only moderately wide when used on a crop camera. The widest zoom available is 16-35/2.8 II, also only moderately wide on a crop camera (only 2mm wider than your kit lens). Keep in mind, by definition all L lenses must be designed to work on all EOS cameas, including full frame cameras, and so are not optimized for use on a crop camera and can't take advantage of significant cost savings possible with lenses designed for use only on the smaller format. Many L lenses are excellent... but a lot of non-L are also very good, can be even better optimized for the smaller format cameras.
You have a lot of very good lenses to choose among...
- Canon EF-S 10-22mm (best all around, and one of the most expensive)
- Tokina 12-24/4 (not quite as good or wide as the Canon, but a lot cheaper... the latest "Mark II" version is a little more flare resistant)
- Tokina 11-16/2.8 (a little sharper than the Toki 12-24, but much more prone to flare & a very narrow range of focal lengths is the trade-off to get f2.8, which may not be necessary for most folks)
- Sigma 8-16 (the widest available aside from fisheyes, strong distortions, rather expensive)
- Sigma 10-20 (two versions: the variable aperture is one of the cheapest, the f3.5 is rather pricey)
- Sigma 12-24 (actually a full frame lens which makes it quite expensive to use on a crop camera, heavy distortions)
- Tamron 10-24 (one of the cheaper, widest range of focal lengths, a bit soft at the 24mm end)
- Rokinon/Samyang 14/2.8 (also sells under Bower, Vivitar, ProOptic and some other brand names... not terribly wide, it's a full frame lens, but affordable because it's strictly manual focus and manual aperture control, so slower to shoot with)
There are some others, as well as some discontinued models, but the above is a pretty good selection.
I have had the Toki 12-24/4 for several years and it's a good lens. I rank it second only to the Canon 10-22mm, which I just bought used and am starting to use and compare with the 12-24.
Have fun shopping!