I wouldn't put a GTX295 in a system with socket 775 and I tell you this from experience because when I bought the GTX295 I plugged it into an E6600 and a P5N32 SLI and it didn't give it everything, it was when I switched to the 920 and the P6T Deluxe V2 and it seemed like I had a new, more powerful graphics card.
As they indicate to you with a GTX480 you have a very similar performance but it's monogpu.
Best regards.
Well yes, I have it in a drawer and I prefer to have a 260 plugged in, it's that even if you put the Q6600 at 3600 it's not worth much, that card is too unstable on 775.
For example a 470 worked much better for me on that system, it's a P45 but the 295 got up to 95º and with the fan at many revolutions, it's nothing like how it goes in a better system, that's why it's better if he wants Nvidia to put a 470,560ti or 570 if he finds them cheap, AMD should also work better for him a 6970 or something similar, the 480 of course performs the same or more and they are found cheap.
they should work better especially much more stable.
Best regards