I have a Dell XPS 8700. I am wanting to get an upgrade to my graphics card. I currently have an AMD Radeon 7570, and it takes up the only video card port on my motherboard. I also have an AMD Radeon 6670 graphics card that I found in my attic.My question is; which would be better? Get a new motherboard with another graphics card slot, or just buy a new graphics card? (Namely a GTX 960 2GB)