This is not really an answer to the question as much as a general advice...If you decide to send the output to the user in the language you consider best for him/her based on GeoIP, browser language etc. make sure it is VERY simple to find the language selection control on the site at all times even if you don't know the language.
There is nothing more annoying than being presented with a site in Hungarian just because you happen to be in the hotel lobby using a computer where you don't have access to the browser settings (unless you speak the language).
Also, despite being a Swede and having Swedish as my first language I almost always prefer an English or German site in English or German in front of a translated one. Important things get lost in translation way too often and as long as the language is not stopping me I know what I prefer. I realize that this is not the "normal situation" for most of your users but please keep us in mind :)