I have a DELL 8300 with 3.0 GHz,4gb of ram and a 128 graphics card. I would like to up the graphics card but DELL is only showing me that I can go up to a 256 (3DFuzion GeForce FX5500 256MB DDR PCI Graphics Card) I am wondering is this true or can I get a 512? I'd like it for some gaming that I have not done in a while and it is slow. TIA BD