looks like a good budget build, gts 450 evga fpb is the saem one my wife uses. good psu to run it. only thing i question is the mobo , no sli support so can't go that route as an option. seems like if you want the most out of a machine you'd want him to have that option down the line
I would say less CPU, more GPU, if gaming is the primary function. Go with an X3 proc and at least a GTX 460 / Radeon 6850 GPU. The ASRock mobo in the Tom's $500 system build is a good place to start. I like your PSU selection better tho.