User groups do not seem to be determined by reputation points alone, I think that the amount of time that you have been a member and the amount of posts you have been thanked for factors in somehow as well, butr I don't know for sure. There are several user groups including Specktra Neophyte, Specktra Cub, Specktra Junior, Specktra Cadette, Specktra Senior, and I think Specktra Socialite. The boxes however do seem to have set point amounts, the first 5 boxes (not counting the one you start with) are 100 points, and the 5 after that are 200 points. HTH!