I think either way his PSU will handle it, since he has a GTS250 right now.
If you want a Nvidia card that will stand alone in its class in terms of bang for the buck performance at $200, look no further than a GTX560. don't get the 550, it actually quite honestly, really sucks. http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=1284226&CatId=3669
This one even comes with a free game.