Quite honestly I would never buy a .cn domain, other than:
1. To protect my other extensions
2. You have business in China
3. Your site is geared towards surfers from china.
I think the .info extension lends more credibility than .cn by far! ... Like Cars.info, Cats.info, webmasterforums.info. Also, being an American surfer, I would be weary on clicking a .cn domain.
Now with what you are doing ...a proxy service for people outside of the US ...the .cn may make sense to do. (if this is who you are gearing it to)
-=Chipmunk=-