Mica, what about listing each MEMBER using a color code system, i.e., bronze=40 posts, silver=60 posts, gold=80 posts, platinum=100 more.
This system should be used ONLY to list actual number of posts. In terms of MEMBERSHIP, I believe that should be determined by the club registration date, and the titles you listed should be assigned accordingly. (It would be really interesting if you were able to combine the two concepts)