Buddy of mine sold his Ninja 500 but took him a while, think he got under 2 grand for it.... best of luck though....
One of my best friends has the Ninja 650 and we will trade off from time to time. There is no comparison, the FZ6R is better in almost every way. Kawi has better brakes and slightly lower center of gravity. Older ones aren't as good and they are UGLY, but i've seen first gen 650s CHEAP! Like $1500 cheap!