If you are looking for a true sport bike, I would suggest any of the 600's from Suzuki, Kaw, Honda or Yamaha. In oarticular, the Suzuki GSXR, Kaw 636, Honda 600RR or F4, and Yamaha YZF R6.
All of thes bike offer quite a bit in a small package. The motors lay down a fair amount of power, the suspension and brakes are top notch, and they are light weight.