That is a good idea, the newer 600's are amazing bikes. You will have to work more to get the speed out of it but you will become a better rider and you will have a lot of fun.

Dont forget that the new 600's still put down 100rwhp completely stock. Any of them will be much faster than your 600 katana. If you have your motorcycle license you can go test ride at a dealership.

Good Luck and let us know what you decide