The 17-40 is a good choice for landscapes - as pointed out, it's a bit soft at f4, but once stopped down, you'll get very good results, and if you're using a tripod, you'll lose nothing from the longer exposures needed. I'm not sure what price it goes for in the US, will $500 be enough? Used?
The Samyang/Rokinon 14mm is a genuine bargain of a lens. It's manual focus, but don't let that put you off - depth of field is so large, it's an effort to get things out of focus! It's very sharp, but does suffer from a peculiar "moustache" distortion. Depending on what you use for post-processing, this can easily be fixed. It can be "too much" of a wide-angle, if you're not used to such a wide-angle perspective. Worth playing with though! I find that I use mine more often in a "portrait" orientation - it begs to be used that way if you have an interesting sky. As a bonus, coma is very low so it makes an excellent lens for nighttime landscapes under clear, moon-less skies - and as the nights are currently drawing in in the Northern hemisphere..
Dustin Abbott reviewed the Rokinon 14mm and started a thread with a link to his review. There are some excellent photos taken with the lens, by Dustin and others in the thread, plus a lens correction profile for Lightroom (on p.12, if memory serves)http://www.canonrumors.com/forum/index.php?topic=17252.0