Best GPU for Dell XPS 9100 with 990X CPU and 24GB RAM?

PC has AMD Radeon HD 6700 Series GPU, can I put a GPU in that will run VR? or what GPU could I use that is MUCH better than present GPU? eBay,etc…

Can anyone help me?

This is a wrong place to ask, but something like GTX 1060 should do fine. The CPU is quite old, but it should suffice.

In the future, you should ask such questions at a specialized gaming website.