Best location for rushed visa application in Seoul?

Hi there - quick and important question! For a U.S citizen (legally residing in Korea) seeking a RUSHED application, where is the best place to go? Not very clear from the information above? Do you visit the Chinese Embassy, the Consular Office or one of the Chinese Visa application centres (CVASC)?

Please confirm ASAP - need to go to tomorrow morning.
Thanks!
G.