So, are you building a rig for your brother? What is the total budget, and what PSU did you get? A cheap one that comes with a case (unless it's one of the Antec Earthwatts) may be good for no more than 60% of its labeled rating before it either turns into a frog and croaks, or its rails go out of spec, possibly damaging other parts.
What kind of computer does your brother have? If it's a dell, hp, or another computer maker model I'm willing to bet money it has a poor power supply, in which case go with the 4670, it doesn't require much power and it's a great card for resolutions of 1280x1024 and under. You can usually get one for around $80-90.