King Cats are great sleds but not for someone his size/weight. Pick up something lighter in the 600/700 range, RMK, Summit, maybe an 05 M6 possibly.
My kid has been riding one since he was 14. First an 03 900 159 then upgraded to an 05 kk.
I agree with you it a lot of sled but at today's prices it's also a lot of bang for the buck. Probably one of the best deals going on used sleds and they are in his price range. Plus he won't out grow it for years to come!
Another good option is the 800 in the same 04 chassis but the 900's are just so plentiful and in stock form only 10hp more.