Re: Help me choose a graphics card!
Like grey said, put a few more dollars and you'll get a 460, less power consumption, more CUDA cores and if you don't really care about DirectX 11, it's good to go (plus 336 cores is far better than 192, almost double the ammout for a few more dollars).
Anyway, anything better than a 7800GTX (the kind of architecture the NVIDIA RSX in the PS3 comes from) might do the trick.
In this case, the overall rule of thumb could be... if your friend is in need or wants some PhysX in his/her games, NVIDIA all the way. Otherwise, choose between the AMD offerings. Any of them will give him/her plenty of fun with any game you toss at it.