Dell XPS 8940 — PCIe x16 slot, but a tight 360W PSU limits your GPU options

The XPS 8940 has a PCIe x16 slot for a dedicated graphics card, but the power supply is typically only 360W or 500W. You can upgrade, but you’ll need to choose a GPU that doesn’t draw more than the PSU can handle — which rules out a lot of high-end cards.