I've driven my sister-in-law's S2000.
Its a real light car. It doesn't get very good gas milage though (about 24mpg). But it really handles. Its real fun to drive because you have to really wind the motor up. The motors almost like a motorcycle engine. You can't think about doing anything, even cruising down hill, under 3K rpm. Normal driving is between 3.5K and 4.5K rpm.
A guy's son at work races against them with his synchro turbo Audi wagon. He says the S2000s are real hard to beat because they are so light and they handle so good.
I'd be looking at that S2000. Even if its a little above the budget.
On the down side, the car has had 2 cracked windows. Debris from the road is always cracking the windshield. And the seats are real low, so if you're like me and like to put your elbow out the window when driving, you'll have the elbow at head level instead of shoulder level.
There's a lot of aftermarket stuff for them, including superchargers. The engine's easy to work on too. Not a cluttered engine compartment. The engine does sit real far aft in the compartment (for better weight distrubution). Honda could have easily put a V6 in it, but because of the weight they went with a V-tec I-4.