6,000 links is a relatively small database for Links SQL, not that it matters :)

Anyway, upgrading won't make any huge speed differences I expect. There are just new features such as reviews (I think that was added after 2.0.4?) and numerous bug fixes no doubt.

If everything is running smoothly then it may be best to leave it - if it ain't broke don't try to fix it....I speak from experience because I always end up breaking "it"