Why are people assuming that if he buys this now he won't have the money to buy another one in 4 years? It seems to me that he could come up with 1/2 the cost of a new one and mom and dad will foot the bill for the other half come college.
Look, I totally get the whole judgmental thing about people looking at a 14 year old kid and his soon to be $1,700 purchase, but times have changed. I didn't have a cell phone until I was 16 and even that was early. My nephew, who is years younger just got his first iPhone. None of us will change this kid's mind so why bother?
I would not personally wait to buy that machine. The discount you're seeing is great and that computer will easily last you through high school. When it comes time for college it will be time for another computer. I wouldn't worry about the processor, it is way more than you need for tasks that you'll be given in high school.