You can upgrade the memory on all dells but you can only upgrade the graphics card if the motherboard has a PCI express x16 slot(PCIEx16).All of the graphics cards you listed are PCIEx16 so yes you can also upgrade the graphics card. The only issue with upgading the graphics card would be the power supply. Most dells have a 300 watt power suply which is fine for the graphics cards dell offers but might not be sufficent for a high performance card like the GeForce 8800GT or Radeon HD 2900 Pro that recomend at least a 400 watt power supply. You would probably need to also the power supply if you upgrade the graphics card.