User Titles

[Chief]

I'm pretty close to that (and changed last to Boosted).
Here's the set-up:

Parked (Minimum Posts: 0)
1st Gear (Minimum Posts: 25)
2nd Gear (Minimum Posts: 100)
3rd Gear (Minimum Posts: 300)
4th Gear (Minimum Posts: 600)
5th Gear (Minimum Posts: 1000)
6th Gear (Minimum Posts: 1500)
Boosted (Minimum Posts: 2000)

Custom titles after 3000 posts...
The increments seem to make decent sense this way.