Looks good.. It shouldn't be too easy, and I like how the margin increases the higher the level. Maybe this could be slightly downsized to make it more attainable..
We could just copy what intense muscle does in regards to names (not the actual relation of post counts):
New Member -- 1 TO 499 POSTS
Bantamweight -- 500 TO 999 POSTS
Lightweight -- 1000 TO 1,999 POSTS
Middleweight -- 2,000 TO 2,999 POSTS
Light Heavyweight-- 3,000 TO 4,499 POSTS
Heavyweight -- 5,000 TO 7,499 POSTS
Superheavyweight-- 7,500+ POSTS
This works out to:
New member -> Bantamweight = +500 posts
-> Lightweight = +500
-> Middleweight = +1,000
-> Light Heavy = +1,000
-> Heavy = +2,000
-> Super Heavy = +2,500
Since this is a bodybuilding forum, I think this idea is awesome. Of course the numbers can be tweeked higher or lower..This is only a rough estimate.