How do you expect to use @font-face with Proxima Nova?
The choices I gave you from Webtype will be expensive (but worth it) if you choose to do a custom-order for @font-face. I just finished up a custom-order with them for the Harriet Series to self-host them. The CSS that comes with it is encoded so no one can steal the files. The reason I did this was because I wanted to own the webfonts, not rent them. The only distributors that allow self-hosting for Proxima Nova is MyFonts, Fontspring and FontShop.