You might like to day dream about winning the Indy 500 or the Monaco Gran Prix, but, in reality, you're way too broke to get there and way too sloppy to survive the experience. That's what autocross is for. The only thing you can crash into is a cone, and cones aren't expensive or life-threatening. 

You should go buy a Miata, because you can afford one, and in the 2009 SCCA Solo 2 Nationals (a big autocross championship), the top 27 of the 33 entries were Miatas.