For your resolution going to a card like GTX460 and next to no gaming would be an absolute overkill!
yeah you are correct, if he does want to game however wouldn't you get a 768mb gtx 460 over a 5770 for the money? I guess it depends on what the ops true needs are but bottom line is for about the same money as a 5770 you can get a 768 mb gtx 460.
And if the op wants real light gaming then both are overkill he should get a gts 430, although depending on the ops actual needs a gts 450 could be a good option too, .maybe a 5670?
In my opinion you kind of have to commit one way are the other as to have gaming capabilities or not but then there is a question of low end, or mid range for the op to decide...