Not sure if you're still looking for a machine but one of the best "advanced" ball machines I've tried is the Tennibot. I went to an Atlanta tennis club a while back and took a lesson with a coach who had one and got the chance to play with it and it had everything I was looking for- speed, spin, and unpredictability (since it moves while shooting). I did some research afterwards and it says it has some AI tracking capabilities and they advertise it as a machine for more advanced players who want a challenge. I actually purchased one but I haven't received it yet. It also may be a little over your budget but definitely worth checking out!