If you're like me, trying to graduate from MX5's to GT4, buy the Porsche.

This thing is the shit you want. I originally tried the Aston Martin and was struggling a lot with the rear-end coming out from underneath me. The Porsche is pretty much glued to the track. You'll notice the difference immediately on your out-lap; you'll actually feel like you can push it. For three weeks driving the Aston Martin I didn't finish higher than 10th. Competed in my first race in the Porsche last night and finished 5th on a track I have little practice on.