I agree, it's very rare that a faster car is going to make you want to drive slower to more thoroughly explore the limits of a car. Take me for a example. I'm a pretty aggressive driver by nature. Back when I had my Camry, I drove the shit out of it, but I never really pushed it as hard as I could, because...it was just a Camry. I knew exactly what would happen if I tried to take a 90-degree right-hander at 40 mph in that car. Then I got my '04 Lancer Ralliart, and suddenly, I was superman! It was considerably sportier than the Camry, and driving it back to back with my friend's Evo, though it obviously didn't perform nearly as well, it had the same kind of feel. Well, it took me a grand total of four days to smash that car into a wall at 78 mph, totalling it. So, I speak from experience when I say that moving up to a sportier car is going to make you want to drive faster.
However, at the end of day, it definitely does come down to the driver. When I get my Impreza last August, I didn't even push it at all for six months. I took it slow, gradually learning how the car reacts to trail braking, feinting, e-braking, etc., because I had learned the cost of recklessness. So, I would strongly advise starting off with a slower car and learning how to control your car before you step up to something like a 300ZX Twin Turbo.