IMO 750 is an odd size. I am not a GIXXER fan by any means, but the 1000 is the way to go. The 750 is going to be faster and have more low end then the 600, but you will get use to it fast and want more. IMO a nice running 600 sport bike is just fine for the street, but then again I would not mind having the low end power of a 1000. The CBR 1000RR is a damn nice bike so is the RC 51 if you don't mind the V-twin engine.