currently riding 03 zx6r, really like the kawasaki feels like you can put it anywhere and be really agressive with it. Loads of fun and feels quicker than all 600's ive ridden. The bike seems like a pocket rocket, a toy. It is small and has race style positioning, but twist that throttle and you are out of their. Only change would be tyres some 208's. The 600rr r6 and gsxr600 are all great bikes to, and will swop for 04 gsxr next year. get some long test rides in and see which bike suits you, i tried all the 600's a few times before deciding.
best of luck.