100% agree, any machine you get for him will be for OFF-DUTY uses.
Find a budget which you are comfortable with and stick to that- There will ALWAYS be a better laptop available, I personally have never spent more than $900 for a machine.
PS- Why are you buying and not him??
He'll be getting free room/board and won't "Have to" buy even clothes. The Army will give him everything he needs, his paycheck will be whatever he wants to use it for.
As a dad of 3, I say it's good sometimes they learn to SAVE and buy stuff themselves. Sure he might want it NOW but counsel him to NOT use a creditcard or loan or payment plan to buy ANYTHING...!