The slowest sportbike, even a 500, will most likely outrun your FAST sportscar. Think about that.
ANY of the 600's will beat most sportscars in acceleration, I guarantee it.
So when you say you want something "FAST", any sportbike is fast, from the 500 to the 1300. Their only limiting factors are their riders--YOU! So don't go around thinking something like a ZX9R is THE bike for you 'cause it's fast. Chances are good you'll crash that thing. I think even a 600 is too fast for someone who's just starting out.
I highly suggest you get a Bandit 600 or an SV650 first. Although even those might be too much for you even if you think you're a "fast learner". It takes at least a year and many thousands of miles to really get good on a bike. When you've only been riding a few months and few thousand miles, and you think you know it all already, that's when something comes back to bite you. Put your ego aside and listen to the veterans that have ridden thousands of miles and have seen many puppies like you crash their expensive sportbikes!