If you’re looking for a relatively cheap, really friggin fun, high-performance but not the way you might think, and super great for riding around town/country, I HIGHLY suggest checking out supermoto. When I first started out, I was super taken by the whole sportbike look, and didn’t really like the look of a “dirt bike.” I still love me my sportbikes, but man, buying a SUMO bike was the greatest decision of my life. Like Allen said, sportbikes just aren’t that much fun to ride on the street; I save my GSX-R for the track. But supermoto bikes? Man…
Supermoto is a form of racing, really, in which you take what was a dirt bike, throw street tires and suspension on it, and then slide it around a tight, super-technical track and absurd speeds (for the track, but not for your safety). As a result of being former dirt bikes, they’re ultra-light and nimble, and they handle really well. Since supermoto started getting really popular, manufacturers like Suzuki, Yamaha, KTM, Aprilia, Husqvarna, and Honda have started producing SUMO bikes ready-to-go. Suzuki’s is the DR-Z400sm (sm = supermoto), which I have, but there are many others to choose from. At least consider it. These bikes are just as fun and WAY easier to ride than the bikes you were considering. The best part is that they’re fun to ride between 20-60mph, which means you can ring their necks without breaking a law. Here’s some badass supermoto riding to entice you (skip to around 1:15):
SuperMoto Junkie has plenty of info for you if you’re interested. I realize this type of bike isn’t for anybody, but most people don’t even know it’s an option.