Wide Angle Lens Question - For using with 5D Mark III

Assuming, I do not need all that wide end (16mm may be fine for me - though I like to get something around 14mm...) and I may not need F2.8, which one would you recommend?

My camera is 5D Mark III. I use 24-105, 70-200 F4 IS, 85mm F1.8 and Sigma 50mm F1.4

Another wide angle that I am looking is Rokinon/Samyang/Bower 14mm f2.8. I do not mind manual focus.

All your suggestions and comments are greatly appreciated.

-Madhu