AI Engine

What AI Engine do you recommend for my game? Our game is a space shooter from the top view, similar to asteroids. It would need path finding around other ships, astroids... And the ships keep moving due to momentum, and turn at natural speeds (not instant).

I found this, but am not sure the best way to go.
http://en.wikibooks.org/wiki/Game_Creation_with_XNA/AI/AI_Engines

I would like an AI Engine that can handle the following:
The main ship
bad guy ships
bad guy ships in formation
asteroids
planet with gravity
AI with learning would be great
bad guys should be able to shoot.