Check out the 20 mm 2.8 or the 15 mm fisheye. Both Canon. Both in your price range. Both 2.8. Both can be considered "wide" on a 7D. I have no experience of these lenses. Maybe someone who has them can share...
I have the 15mm fisheye and though it's probably the best fisheye on the market for full frame, I would not recommend it on a crop sensor : you'll end with a 24mm equivalent with tons of distortion. The 20mm is probably not a very good solution either, some people hate it, some like it, but it's an old and big lens that'll give you only a 32mm equivalent, not very wide.
The only crop sensors I had were Nikons, but when I had to find a wide angle, I came to the conclusion that a dedicated crop sensor lens is the way to go. I had the 12-24mm f4, and it was an excellent lens.
Crop sensors are as good with tele lenses as they are problematic with wide angles. One of the important reasons for using full frame sensors is precisely when you need a choice of wide angles.
I would suggest you stick with the Canon 10-22mm or the Tokina 11-16mm that has an excellent reputation. You will have a real wide angle zoom, with much more flexibility than a fixed one. Even the Samyang 14mm would give you "only" a fixed 22mm with manual focus, compared to the equivalent 16mm of the Canon zoom.
My guess is the Canon would be bright enough with increased ISO (you can get a sharp picture with 1/15s), otherwise the Tokina is the way to go, IQ and built quality is excellent.
Edit : not that I am a big fan of Ken Rockwell, but you should nevertheless have a look at his review of the Tokina 11-16mm f2.8.http://www.kenrockwell.com/tokina/11-16mm.htm