The classification for AAA is a dollar range. I don't know the exact ranges (someone no doubt will come along that does).
After you draft you 25man roster, an expanded draft area will magically appear, and you can select your AAA players. All players not in the classification range are automatically blacklisted, so anything you see, you can have.
Sometimes its helpful to see what is available in the AAA database before you draft your 25man roster. You can accomplish this by simply uploading a predetermined team (like the 2010 Angles for instance) and jumping right in to the AAA. Then erase the crappy Angels and draft who you want. I can't remember if the AAA players are erased as well when you do that, so you might want to write them down.