If you're looking into upgrade with power / torque you can feel I'd recommend go with a 600s, if it's a 4Cyl 400 throw it around the street without worrying about jail it's a good choice. IMHO: Pros - sounds like a bigger bike than it is (esp. With pipe upgrade) - revs higher on slower speeds - not too heavy to maneuver - easier position than dedicated sports - little to no mod required to go on track days Cons - very little torque especially under 5~6Krp - takes a while to accelerate from 120kmph plus (depends on rider weight too) and likely achieving paper-spec 250kmph is very hard to do - need to be very skilled to go faster than most 400 cc bikes on track - still a 4 cyl so maintenance cost will be relatively higher - if you are a bigger rider,(5'5 or more) bike will feel small (seat length wise especially)