The rules are ok. Getting refferals is a pain sometimes but... 18 isn't such a big number(for 500 posts).
But some other rules should be placed like: what kind of posts you'll take into consideration for the post count.
I don't want someone to get mad at me, but the posts in the subforum "introduction" should not count for the post count. I mean... i can easily get about 90 more posts to my post count (made 4-5 or more posts there myself ) by just saying hi/welcome to everyone there.
Otherwise i'm pretty happy with the rules.

__________________
Get cheap Logo's/Banners/Flyers - CLICK ME