For which PC should i get a graphics card for?

Get it for the first one, the second one has a far too weak processor and not enough ram and it sounds older than the first one. Having a PCI graphics card in the first computer is much better than having an AGP graphics card in the second computer as the second computer is way too weak to run them games anyway. So get the first one. And you can't move the processors around because one system runs on AMD chipsets and the other runs Intel chipsets.