DONT BUY ANYTHING!!!!! except a good helmet and warm gloves or mittens and thin ski socks (not tube socks).
Go to the local ski shop and do a seasonal lease. You can lease new or used stuff. Look at the used stuff first, often times it has never been used or used 1-2 times (not so with adult rentals). We leased use stuff that was so barely used the top sheets weren't even scratched!
My 9 year old daughter is 53" tall and 60 pounds. She started skiing two seasons ago. Last season AND this season we had to exchange the boots because she outgrew them mid-season. Skis...she started on 117's, last season 120's, this season 125's.
My point, unless he is an olympic protege, requiring the "best" gear to remain competitive, it is not worth buying. He will outgrow what ever you buy him so fast you will be throwing away money. Lease decent stuff and exchange it as he grows.
I mean no offense here, but at your sons skill level there is not going to be an issue with brand. Generally speaking the ski should come to his lower lip. The ski shop wil size him for boots and skis. Make sure, spend time in the store (bring a video game, magazine, etc...) to make sure the boots are comfy. Have him wear them for a while in the store to make sure they do not cause cramps or soreness. If his feet are not comfortable, he will not enjoy skiing...regardless of which ski you get him.