Well the main use for the machine will be games,movies,music.
A friend of mine has this video card and he can play Crysis on max settings with resolution of 1024x768(not sure about the resolution) so why is it bad for gaming?
What resolution will YOU be using?
And your friend will be playing a low settings, even at that resolution, a terrible waste of a truly beautiful game.
I would suggest the HD4670/9600GT/9600GSO as a maximum, anything more will need a more powerful powersupply.
If the PSU has a 6 pin PCI-E connector, yes, the 9600GT will run.
If the PSU does not have a 6 pin PCI-E connector, get the HD4670 instead or you'll need to use molex/PCI-E power adaptors, which should be avoided like the Plague.