Just make sure to get seat time on the kfx before you let the 660 go. I sold my kfx450r after a year due to its very tight riding position, hard seat and long efi starting sequence. I went to a 660r and could not be happier. They are light bikes but like to eat clutch baskets. If you like standing up to ride or mx then the kfx is good. I hated mine in the woods and hill climbs