I'm running on a second machine a GTX560SE (it's in the same category as the 7770 or 460) with an E8400 at stock though. The problem is that there is an increasing number of games which like strong CPUs, more cores/threads the better, speed and DDR3. Such a game is BF3 multiplayer which is basically unplayable due to the CPU/RAM that I have (single player is stuttering but acceptable) even if the GPU can handle it at lower settings.
On the other hand there are plenty of good games that run very well with such a setup. The idea is that the bottleneck is unavoidable when you play games that need CPU horsepower whatever card you have. So my advice would be to keep the costs reasonable and give him the 460 (though a 1GB GTX460 would be better).