I originally looked at the CBR600s, I don't think you can go wrong with a Honda but I had a close friend that wanted to sell his 300 because he upgraded to a Yamaha 600. I've always wanted one so I agreed to buy his 300. I assume someday I'll upgrade but this is perfect for me right now.
Kawasaki zx6r is a 636. I wish I had a Ducati, I want the 1199 lol but it's like $27k which I don't exactly have laying around even the 899 is like $15k new at least