Can I upgrade my old computer video card?

Episode 1565
Jeff fromJeff has a ten year old Dell XPS computer and it still works great. However, the newer games are only DirectX11 compatible and Dell says he has to get a new computer. Is there a card for him out there? The power cables are 6 slot and the new ones require 8 slot. Leo says he can get an adapter, but that age computer means it will be PCI, whereas the latest video cards are PCIExpress. Modern games use both CPU and GPUs in concert. And Jeff's power supply is probably underpowered.