your friend is a dork. Thats a good match. You dont want anything lower than a gts250 if you want any kind of future proofing for your gaming system. I would opt for an ati 5750 for roughly the same price though, its a bit faster in most games, supports dx11 and uses less power. I think when it comes to gfx cards, you always want to over-do it a little bit so they dont become outdated so quickly.
Its like throwing a HD5870 for 1080P, nice but overkill.
For even 1366*768, the 5670 is a nice choice, will yield at least 30+ fps for even the latest games, after all he can always upgrade. Though for the money, the 4850 seems great , its more or less the same price as the 5670 for 5750 like performance.