S2 weapons have no rating requirement. I'll have my precious mage staff soon at a paltry 1605 rating. w00t!
FWIW, along with the S3 weapons, the S3 shoulders will have a rating requirement as well, and I believe it's actually higher than the weapon requirement, but don't quote me on that. Note that these rating requirements will be your "personal" arena rating, not the avg of your team ratings or the highest of your team ratings, etc. I believe the personal rating system will be based solely on the matches in which you particpated.