My son has been playing on a rented king 660 for two years and he really likes it. We want to buy him a sax vs. continue renting but our budget prohibits buying something new. A lot of blogs sing praises of king 613, but I noticed it doesn't have the high f sharp key that is on the king 660 he's been renting. Also, he is confortable with the king 660 since he's been playing it. I found a king 660 online out of state from a reputable music store for a good price and they will ship it to me. I also found a king 613 at a more local reputable music store that we can go down and try out. The price is about the same for the king 660 and the king 613. Does anyone have an opinion on which we should buy? On one hand, I lean toward the 660 because he's familiar with it and because of the extra key, but am nervous about buying out of state. On the other hand, I feel better that he can try out the 613 before buying it but I am concerned it is a lesser sax for the same money since it's missing that key. Does anyone know more about the differences between the two sax models and what would be best for a 6th grader entering middle school?