ill tell you what i know, you want a car that offers a communicative ride.
One that tells you how close the car is to its limits. Without this, your room for error is very small, and more often than not, you WILL end up off the track. It needs to be stiff, but not too much. Your goal is to maintain maximum contact patch throughout the whole track, using every little bit of straightaway and charging out of turns with a smooth finese.
And i wouldnt even sa you need 250 hp. Hell, in autocross, a slong as you have the torque to pull you out of turns, you should be fine( as a beginner...)