here is my 2cents worth right here. First Get rid of that stock 300w ps. It is more than likely a generic one that will last him if he is lucky a year at most.
Now, with that being said here is what I think you should get for him.510W PS
this is rather Pricey, but believe me when I say that in the long run he will thank you for it, and this PS will have a 5yr warranty attached to it